docs(decisions): refinement-pass resolutions — audit tier-gate, bulk_class projection, two-layer streets

From the Si refinement of the Phase-4 fill-seam tickets. D-097: the mandatory-check gate keys on ComplexityTier, not WorldTier (wording fix). D-233: bulk_class is the 8->5 built-form projection (the 8 cargo-types stay on commodities); a settlement's dominant commodity is derived from its production chains, not an authored role->commodity table. D-234: streets are two-layer — MST arterials (Civ6-style, the guarantee-audit graph) + +/-45deg grid local streets (Civ4-style); Voronoi rejected (breaks +/-45 + the axis-aligned footprint fast-path). Ticket-level refinements (foundational types task, era-gating fix, catalog resequence) live in the ticket DB.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

decisions/architecture.md

@@ -266,7 +266,7 @@ Technical foundation decisions that constrain implementation: engine, client-ser
 - **Raised by:** Gestalt (tier structure + assassin lens integration), Tyre (GuaranteeAuditResult struct). Full team sign-off.
 - **Dissent:** None.
 - **Cross-reference:** D-103 (assassin lens guarantees A-1 through A-4), D-102 (horizon view corridor — Tier 2 coastal)
-- **Amended 2026-05-25 (D-229/D-231 — guarantee-audit engine hook):** The audit runs AFTER step-3 fill completes for a district, before the skeleton is marked "complete"; on a failed mandatory check for the district's `world_tier`, fill regenerates with adjusted parameters. Signature: `run_guarantee_audit(skeleton: &DistrictSkeleton, building_tags: &[BuildingPropertyTag], street_graph: &StreetGraph, seed: SeedChain) -> GuaranteeAuditResult`. Tier-1 checks (all inhabited): `social_hub_present` (≥1 building with entry_class ∈ {Public, Commercial} AND zone ∈ entertainment/market/transit); `informal_zone_present` (≥1 Organic + Public, or open ground in an Organic district); `encounter_corridor` (street graph has a continuous Public traversal path crossing the district). Tier-2 checks (full-complexity): `traffic_chokepoint` (a bottleneck node whose removal disconnects the graph); `institutional_space` (admin/judicial/checkpoint, Restricted); `insider_space` (Restricted + Hidden or non-primary-street door); `economic_node` (≥1 Commercial); `breach_only_zone` (≥1 BreachOnly). Tier-3 / A-1..A-4 (pure graph/geometry over step-3 tags + street graph — NO interior generation): A-1 elevated vantage (max above_ground ≥3 with unobstructed LOS to a chokepoint); A-2 egress multiplicity (≥2 distinct unique-street connections across the perimeter); A-3 temporal opacity (≥1 TemporalWindow door → reduced traffic in closed hours); A-4 non-institutional route (a Public→insider-space path exists that avoids all institutional buildings). `GuaranteeAuditResult` gains a bool per check above, retaining its existing `rooftop_discovery_zone` (D-106) and `horizon_view_corridor` (D-102) fields. Raised by: Gestalt, economic-built-world workshop round 2.
+- **Amended 2026-05-25 (D-229/D-231 — guarantee-audit engine hook):** The audit runs AFTER step-3 fill completes for a district, before the skeleton is marked "complete"; on a failed mandatory check, fill regenerates with adjusted parameters. **The mandatory-check set is keyed on `ComplexityTier`, not `WorldTier`** (T1 = all inhabited; T2 and T3/A-1..A-4 = Full only). Signature: `run_guarantee_audit(skeleton: &DistrictSkeleton, building_tags: &[BuildingPropertyTag], street_graph: &StreetGraph, seed: SeedChain) -> GuaranteeAuditResult`. Tier-1 checks (all inhabited): `social_hub_present` (≥1 building with entry_class ∈ {Public, Commercial} AND zone ∈ entertainment/market/transit); `informal_zone_present` (≥1 Organic + Public, or open ground in an Organic district); `encounter_corridor` (street graph has a continuous Public traversal path crossing the district). Tier-2 checks (full-complexity): `traffic_chokepoint` (a bottleneck node whose removal disconnects the graph); `institutional_space` (admin/judicial/checkpoint, Restricted); `insider_space` (Restricted + Hidden or non-primary-street door); `economic_node` (≥1 Commercial); `breach_only_zone` (≥1 BreachOnly). Tier-3 / A-1..A-4 (pure graph/geometry over step-3 tags + street graph — NO interior generation): A-1 elevated vantage (max above_ground ≥3 with unobstructed LOS to a chokepoint); A-2 egress multiplicity (≥2 distinct unique-street connections across the perimeter); A-3 temporal opacity (≥1 TemporalWindow door → reduced traffic in closed hours); A-4 non-institutional route (a Public→insider-space path exists that avoids all institutional buildings). `GuaranteeAuditResult` gains a bool per check above, retaining its existing `rooftop_discovery_zone` (D-106) and `horizon_view_corridor` (D-102) fields. Raised by: Gestalt, economic-built-world workshop round 2.
 
 ### D-099: WallBackside / TileBehindState — Dual Classification
 - **Date:** 2026-02-27
@@ -1649,6 +1649,7 @@ Technical foundation decisions that constrain implementation: engine, client-ser
   - **Residential follow-on:** every non-residential production block emits a labor-demand signal sizing adjacent residential blocks (BulkSolid extraction ~3.0× → BulkLiquid ~2.5× → Perishable ~2.5× → PrecisionDense ~2.0× → NonPhysical ~1.5×); housing character from `prosperity_baseline` (>0.7 market-rate → 0.4–0.7 standard worker → <0.4 company barracks/squatter).
 - **Frozen-amber:** the vocabulary is t=0-derived and immutable; the condition overlay (D-198) paints Maintained/Worn/Abandoned but **cannot change a `BuildingTag`** — a mine processing plant becomes an *abandoned* mine plant, never an office.
 - **Amends D-199** (adds `dominant_bulk_class`, `dominant_production_ubiquity`, `morphology_zone` to `CityGenerationContext`) and **D-184** (back-fills the `bulk_class` enum values it named but left open). Enforcement: `fill_chunk(ctx, seed)` holds no `PressureState` reference.
+- **Refined 2026-05-26 (batch refinement):** `BulkClass`'s 5 values are **built-form archetypes** — a projection of the 8 commodity cargo-types in `commodities.toml` (`bulk`/`standard`/`compact`/`oversized` → `BulkSolid` [size is orthogonal to bulk-form; a future axis if it earns visual payoff], `precision` → `PrecisionDense`, `liquid` → `BulkLiquid`, `perishable` → `Perishable`, `non_physical` → `NonPhysical`). The 8 stay on commodities for the economic model — no fidelity is lost; the 5 are only the built-form driver. The settlement's **dominant commodity is *derived*** from its highest-output location-bound production chain (D-178), **not** an authored role→commodity table — so the built form reflects the already-authored production/trade data (where sector specialization lives) and varies body-to-body for free.
 - **Rationale:** Floor-area-to-output ratio is the capital structure of an industry, not a style choice — services maximize floor, bulk extraction is mostly open operations surface. Driving coverage and vocabulary from `BulkClass` makes settlements that share an economic *role* look physically distinct by *what they make*, and the ubiquity rule gives the settlement its identity (a MonopolySource town vs background infrastructure).
 - **Implementation:** Phase 4+. `bulk_class`/`production_ubiquity` lookups added to the economics import; consumed in the plan phase (D-230).
 - **Raised by:** Burnelli, economic-built-world workshop round 2, 2026-05-25.
@@ -1663,6 +1664,7 @@ Technical foundation decisions that constrain implementation: engine, client-ser
   - **(a) Permitted street patterns by morphology** — a lookup that gates the D-215 archetype arrangement patterns: fjord/canyon → ribbon or hub-and-spoke only (streets linear along the terrain axis, radial impossible); delta/braided → hub-and-spoke following channels (bridges as forced nodes); alluvial-plain → any pattern; island → hub-and-spoke (perimeter access priority); mountain-pass → ribbon only (elevation steps as block boundaries).
   - **(b) Waterfront footprint rule** — any block adjacent to a water morphology feature uses **pier/quay geometry** on the water-facing edge (no standard setback, dock-orthogonal subdivision, access priority toward the water) and standard street frontage on inland edges. Applies uniformly wherever a block touches a water feature — body-independent, zone-independent. This is what makes port towns present to the quay differently than to the street.
   - Street geometry obeys the ±45° pathfinding cap (D-096) — no curves; straight lines appear only where authored (the D-228 cohesion rule). Fills the Step-1 `chunk_layout` / `corridors` / `access_points` stubs.
+- **Refined 2026-05-26 (street-network algorithm — two layers):** streets generate in **two layers**, mirroring real cities and the Civ road lineage. **Arterials** (`corridors`) = a **minimum-spanning / least-cost graph** over the district's key nodes (access-points, reservations, landmarks) — emergent trunk topology (Civ6-style, "roads where traffic wants to go"), ±45°-snapped; **this is the node/edge graph the guarantee audit (D-097) reads** (a chokepoint *is* an arterial bottleneck; an encounter-corridor *is* an arterial through-route). Ribbon = MST on linearly-constrained nodes; hub-and-spoke = MST with a forced centroid hub. **Local streets** (`chunk_layout`) = a ±45° **grid lattice** within each block (Civ4-style), modulated by the D-096 Grid/Organic mode (offsets + rotation). **Voronoi was rejected** — its arbitrary-angle edges violate the ±45° cap and its irregular cells break the axis-aligned `TileRect` footprint fast-path (D-229), degrading per-chunk fill from rectangle-containment to polygon rasterization. (Civ1–4's "road on every tile" is the anti-pattern this avoids; the arterial/local split is the city-scale fix.)
 - **Rationale:** Morphology zone and `architecture_flavor` were added to the context (D-199) as *inputs without consumers* — two economically-similar bodies otherwise produce topologically identical street networks and identical block subdivision (Nigel's same-y-grid failure). These two rules give morphology structural teeth so the fjord port and the delta port are categorically different cities, not reskins.
 - **Implementation:** Phase 4+. Consumed in the plan phase (D-230) when laying streets and subdividing blocks.
 - **Raised by:** Nigel, economic-built-world workshop round 2, 2026-05-25.