feat(simulation): grassland biome-awareness + alien-ecology vocab (T-1085 workstream 4, D-246)

The mosaic palette gains a climate-biome dimension for the Grassland surface-class:
savanna / temperate / boreal / tundra now read distinctly rather than collapsing to
one biome-blind palette (the D-246 biome-awareness fix).

- atlas/mosaic.rs: ClimateBiome (from temperature_c + moisture_q) + four biome-keyed
  Grassland palettes; palette(class, biome). Savanna carries scattered Forest copses,
  tundra carries lichen + sparse bare ground and no forest. §8-safe (veg + water only).
- atlas/voxel.rs: derive the biome; a cold barren district (tundra/boreal) now takes
  the sparse mosaic rather than staying blank — worlds that read "0 vegetated / blank"
  now read structured-sparse (D-245 climate-appropriateness). vegetated_districts
  8→20 and 0→39 on the cold validation bodies.
- data/mosaic_constants.toml: biome-keyed grassland mirror.
- docs/design/alien-ecology-vocabulary.md: Miri's full biome × register naming layer
  (the cane/vane/wrack/husk/drum-root native lexicon + Earth-register names) — the
  derived-label source for the palette and Phase-5 rendering.

Believability golden regenerated. Full server suite green. Forest biomes and the
introduced-Earth register are the noted continuation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/design/alien-ecology-vocabulary.md

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+# Alien-Ecology Vocabulary — micro-habitat naming layer (D-247 / D-246 / T-1085)
+
+Authored by **Miri** (T-1085 workstream 4), 2026-07-03. This is the **naming /
+rendering** layer that skins the mosaic's semantic micro-habitats (T-1084, D-246).
+The mosaic selects **D-228 axis-triples** (terrain × vegetation × water); this table
+supplies the **display names** per `climate-biome × register × niche`, so a "canopy"
+niche in a temperate forest reads as *vane-cane stand* (native-mirror) or *dense
+stand* (introduced-Earth). Names are **derived labels** (D-228) — never stored on the
+voxel. Co-maintenance with **Araminta** for visual grammar (per the T-995 ObjectTag
+precedent).
+
+Governing canon: [D-247](../../governance/decisions/content.md) (native biospheres +
+chirality), [D-246](../../governance/decisions/architecture.md) (the mosaic that
+consumes this). Determinism: this vocabulary is part of the deterministic input
+surface once wired — fix it before the mosaic generates its first world.
+
+---
+
+## Methodology
+
+### Niche spine (the cross-biome authoring scaffold — reinterpreted per biome)
+
+The five niches are **roles**, not literal "trees exist here" claims — each biome
+reinterprets them (a grassland's "canopy" is its tallest grass stratum):
+
+- **canopy** — the biome's tallest/densest cover stratum. Full overhead concealment
+  where the biome has one; the thickest topmost growth otherwise. Blocks sightlines +
+  weather; sets the movement-sound baseline.
+- **understory** — the layer beneath/within canopy, or a secondary partial-cover
+  stratum where there's no true canopy. Partial concealment, filtered light.
+- **wet-hollow** — moisture-conditioned low point, tied to the `voxel_relief`
+  micro-thalweg (D-246). Slows movement; sound and smell carry differently.
+- **pioneer** — colonizing / disturbed / regrowth ground; first-succession or edge
+  margin. The "in-between" transition zone.
+- **bare-ground** — minimal-to-no cover, exposed substrate. Best sightlines, least
+  concealment, fastest movement; the biome's "clearing"/"pan" default.
+
+### Register naming
+
+- **Introduced-Earth** — ordinary recognizable agricultural/ecological English
+  (orchard, pasture, hedgerow): warm, human-scaled, legible at a glance.
+- **Native (alien)** — built from a small recurring invented growth-habit lexicon (the
+  alien equivalent of "tree / grass / moss / reed" as informal field terms, not formal
+  taxonomy — Solandar's "five kingdoms" stays deliberately unnamed at the formal level).
+
+### The native growth-habit lexicon
+
+| Root | Fills the role of | Typical niche |
+|---|---|---|
+| **cane** | tall, upright, single-or-clustered stalks | canopy / understory in wooded biomes |
+| **vane** | broad, blade-like, often iridescent structures | canopy (the richest biomes) |
+| **wrack** | low, spreading, mat-forming growth | bare-ground / pioneer / understory |
+| **husk** | bulb/pod-bearing, clustered near water | wet-hollow |
+| **drum-root** | colonial, ring-spreading root-network | pioneer (recurs across Grassland/Tundra/Savanna) |
+
+A few names deliberately **recur across biomes** (husk-fall tangle, lichen-scald flat,
+scorch-bloom flush, the drum-root/ring motif) — intentional coherence: it reads as one
+designed ecology, not eleven unrelated ones. This is the Bobiverse "convergent-but-alien
+niches" touchstone made concrete: the same growth-habit fills the same niche across
+biomes, as oak/pine/baobab all fill "canopy" on Earth without being the same species.
+
+### Sensory discipline — the achiral seam (D-247) stays intact
+
+Native water is always safe to drink, ground always safe to mine/walk, biomass always
+safe to burn/build. Every note flavors **strangeness** (smell, sound, texture, footing),
+never *danger*, for those actions. Where hazard flavor appears it is **mechanical/
+textural** (brittle husks giving way, thorns, uneven footing) — never biochemical
+(Mirror life can't infect or poison; Compatible hazard is an *authored* option, flagged
+as a hook, not exercised on any specific world here).
+
+### Scope
+
+This table fills **climate-biome × register**, richest on the six vegetated biomes,
+lighter on the five extreme ones (niches merged where they don't naturally apply). A
+full `climate-biome × surface-class × register` cross-product is a future pass; the
+D-246 Sand/Rock/Gravel/Lava surface-class rows already carry register-neutral flavor.
+
+---
+
+## Rich biomes
+
+### TropicalWet
+*The Solandar register — hot, wet, maximum biomass, fast decomposition. "Twelve thousand species, five kingdoms."*
+
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Canopy | **Vane-crown stand** — towering oil-sheened vane-blades interlock into a solid ceiling; understory twilight-dim at midday. A thick sweetish rot-and-sap smell that never clears. | **Cacao shade-block** — planted tree-crop under managed shade canopy; rows just regular enough to give away human hands. |
+| Understory | **Wrack-drape thicket** — wet curtains of wrack draping from the canopy; clings and slows movement, leaves a faint chemical tang. | **Shade-coffee row** — broad-leafed cultivars beneath the plantation canopy. |
+| Wet-hollow | **Husk-seep hollow** — bellied husk-growths at a warm standing seep; water runs faintly opalescent with alien tannins — safe to drink, unmistakably not Earth's water by the smell. | **Rice-paddy terrace** — flooded cultivated wet-ground rows. |
+| Pioneer | **Scorch-bloom flush** — fast alien color-succession flooding a canopy-fall light-gap within weeks, before slower vane-forms retake it. | **Cassava clearing** — a slashed-and-fallow plot gone to quick Earth pioneer weeds and root crops. |
+| Bare-ground | **Salt-crust flat** — mineral-crusted open patch where nothing native roots, by chemistry not disturbance; wrong-colored crust crunches underfoot. | **Threshing yard** — bare packed earth cut into the plantation. |
+
+### TemperateForest
+
+| Niche | Native-Mirror | Introduced-Earth (existing D-246 baseline) |
+|---|---|---|
+| Canopy | **Vane-cane stand** — cane trunks crowned with stiff, faintly metallic-blue vane-fronds; a dry clicking rustle, not a hiss — it doesn't *sound* like a forest. | **Dense stand** |
+| Understory | **Wrack-frond undergrowth** — knee-high tangle, cool and slightly rubbery; brushing it releases a sharp resinous smell with no Earth analog. | **Fern undergrowth** |
+| Wet-hollow | **Husk-reed run** — husk-reeds trace the brook's micro-thalweg; husks pop and refill audibly as current passes — heard before seen. | **Brook** |
+| Pioneer | **Husk-fall tangle** — collapsed cane-husks, brittle and hollow rather than woody; lighter to move than deadfall but sharper underfoot (a footing hazard, not a fire-fuel one). | **Deadfall** |
+| Bare-ground | **Bloom-scald clearing** — kept open by an allelopathic wrack that poisons competing roots (achiral-safe to walk, just barren); faint bitter-almond air. | **Glade** |
+
+### TemperateGrassland
+
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Canopy | **Cane-tassel sweep** — waist-to-shoulder cane tipped with heavy seed-tassels; moves in slow grass-like waves, but the tassels chime softly against each other. | **Tussock** |
+| Understory | **Wrack-bloom understory** — a low flowering layer threading between the cane-tassels; a sweet "almost right" smell that unsettles Earth-register visitors. | **Wildflower** |
+| Wet-hollow | **Husk-line seep** — the ephemeral channel lined with squat husk-forms that only surface after rain — a visible tell of where the water runs even in dry season. | **Dry wash** |
+| Pioneer | **Drum-root knot** — a knotted ring of colonial root-growth pushing up through the grass, spreading centimeters a year; the ring's center is always slightly bare. | **Scrub island** |
+| Bare-ground | **Hardpan scald** — a mineral-crusted bare patch; the ground rings slightly hollow underfoot. | **Grazing pan** — bare-trodden earth from stock. |
+
+### BorealForest
+
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Canopy | **Rime-vane stand** — slow, frost-hardy vane-cane holding a permanent rime-like bloom even in summer; dim, cold, nearly silent — a "wrong" quiet. | **Spruce-shadow stand** — conifer-analog, deep cold shade, needle-duff footing. |
+| Understory | **Wrack-moss carpet** — thick spongy wrack holding meltwater like a sponge; boots sink and release a cold mineral smell. | **Bilberry scrub** |
+| Wet-hollow | **Husk-bog muskeg** — waterlogged cold ground where the tussocks are husk-forms; each step risks a hollow husk giving way. | **Muskeg fen** |
+| Pioneer | **Husk-fall tangle** (shared with TemperateForest) | **Deadfall** — cold-climate blowdown. |
+| Bare-ground | **Lichen-scald flat** — thin pale native crust over permafrost-like ground, ancient and slow; disturbing it outlasts a human lifetime. | **Burn scar** |
+
+### Tundra
+*Treeless, thermokarst. Thin biomass; niches all present but small.*
+
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Canopy (dwarf) | **Husk-heath brake** — the tallest native growth is ankle-high, a dense husk-mat; reads as heath at distance, clearly not-leaves up close. | **Dwarf-willow brake** |
+| Understory | **Wrack-lichen mat** — a thin crust; grows so slowly that a season's footpath shows a decade later. | **Moss-sedge mat** |
+| Wet-hollow | **Thermokarst husk-pool** — a collapse-and-thaw pool ringed with husk-forms that emerge only in the brief thaw window — seasonal in a way no other biome's wet-hollow is. | **Thaw-pond sedge** |
+| Pioneer | **Drum-root ring** (shared motif, at tundra scale — centimeters across after decades) | **Gravel scar** |
+| Bare-ground | **Lichen-scald flat** (shared with Boreal — here over patterned-ground polygons) | **Frost-heave flat** |
+
+### Savanna
+*Warm, seasonal, grass-dominant with scattered tree-copses.*
+
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Canopy | **Vane-crown copse** — an isolated stand, the only real shade for kilometers; mistakable for a gallery copse at distance, but the bark-analog is smooth and faintly warm. | **Gallery copse** |
+| Understory | **Husk-thorn scrub** — thorny native scrub, identical obstruction/concealment to acacia; the thorns are hollow and whistle faintly in wind. | **Acacia scrub** |
+| Wet-hollow | **Husk-pan waterhole** — seasonal flood-and-dry; dormant husk-forms visibly "wake" within days of the first rain. | **Seasonal waterhole** |
+| Pioneer | **Scorch-bloom flush** (shared with TropicalWet — succession by seasonal fire) | **Burnt-grass flush** |
+| Bare-ground | **Drum-mound flat** — a hardpan clearing built by colonial drum-root activity; bare, sun-baked, faintly warm underfoot even at night. | **Termite-pan clearing** |
+
+---
+
+## Lighter biomes (extreme classes — niches merged/noted where they don't apply)
+
+### Desert
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Canopy ("tallest thing here") | **Cane-spire stand** — sparse deep-taprooted spires, each commanding the horizon with a thin moving shadow. | **Date-palm draw** |
+| Understory + pioneer (merged) | **Wrack-thorn scatter** — sparse widely-spaced domed clumps hoarding moisture. | **Scrub flat** |
+| Wet-hollow | **Husk-spring hollow** — a rare seep ringed with water-swollen husk-forms; the local landmark. Water fine to drink; nothing in the ring looks edible. | **Wadi oasis** |
+| Bare-ground | *served by the D-246 Sand/Rock rows* (dune crest, hardpan, outcrop, scree) — bare rock/sand carries no register. | (same) |
+
+### Alpine
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Canopy (treeline fringe) | **Wind-cane fringe** — wind-flagged, permanently bent one way; the flag-shape wayfinds like krummholz, the material reads wrong up close. | **Krummholz fringe** |
+| Understory + pioneer (merged) | **Wrack-cushion field** — tight ground-hugging growth, faintly warm to bare skin (a metabolic-heat tell Earth cushion plants lack). | **Cushion-plant field** |
+| Wet-hollow | **Husk-melt seep** — seasonal meltwater seep, husk-forms present only weeks a year. | **Snowmelt sedge** |
+| Bare-ground | *served by the Rock rows* (outcrop/scree/talus/ledge/**lichen** — lichen doubles as this biome's dominant cover). | (same) |
+
+### Volcanic
+*D-210 flags this the least data-grounded biome; the Lava surface-class already has the richest table. Kept light.*
+
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Recovering slope (canopy/understory collapsed) | **Husk-root slope** — pioneer husk-root colonizing cooled ash, first native life back after a flow. | **Ash-orchard slope** — Earth fruit trees on fertile volcanic ash. |
+| Wet-hollow | **Husk-vent seep** — a geothermal seep, the hardiest husk-forms in the register; warm, safe to bathe in. | **Hot-spring terrace** |
+| Pioneer + bare-ground | *served by the Lava rows* (fresh sheet, weathered crust w/ Lichen, tube collapse, pioneer scrub). | (same) |
+
+### Wetland (climate-biome)
+*Heavily overlaps the surface-class Wetland table (richest baseline). Native mirror given for symmetry; kept light.*
+
+| Niche | Native-Mirror | Introduced-Earth (existing D-246 names) |
+|---|---|---|
+| Canopy | **Husk-crown copse** — water-rooted husk-trees hung with drip-tendrils. | **Copse** |
+| Understory / bare-ground | **Wrack-flat clearing** — open wrack-carpeted shallows. | **Meadow / Clearing** |
+| Wet-hollow (×3) | **Husk-bog / Husk-marsh / Husk-run** — the marsh variant's reed-analog hisses faintly when disturbed, a natural detection tell. | **Bog / Marsh / Creek** |
+| Pioneer | thin/underdeveloped (same gap as the baseline) | (same gap) |
+
+### CoastalLowland
+| Niche | Native-Mirror | Introduced-Earth |
+|---|---|---|
+| Canopy | **Vane-palm fringe** — salt-tolerant, leaning permanently seaward; same visual tell as a coastal treeline, different material. | **Coconut fringe** |
+| Understory + pioneer (merged) | **Wrack-tangle scrub** — salt-hardy tangle; smells of ozone and brine-that's-not-quite-brine. | **Dune scrub** |
+| Wet-hollow (tidal) | **Husk-tide flat** — husk-forms seal shut at low tide and visibly "breathe" open as water returns — a legible tide-state tell. | **Salt-marsh flat** |
+| Bare-ground | **Husk-shard beach** — the tideline wrack is broken husk-fragments instead of shells; the wrong shapes up close. | **Shell-sand beach** |
+
+---
+
+## Open hooks (Miri, T-1085)
+
+- **Five kingdoms** — Solandar's "twelve thousand species across five kingdoms" is left
+  formally unnamed (deliberately-vague canon). Naming the kingdoms is a future hook.
+- **Compatible-world hazard** — a Compatible (levo) biome (TropicalWet, Savanna) is the
+  right *register* for a future authored native pathogen/toxin (D-247 §"coupling permits
+  but doesn't force"); a hook, not yet exercised.
+- **Full cross-product** — climate-biome × **surface-class** × register (this table is
+  climate-biome × register only) is a future pass.