refactor(simulation): remove superseded skeleton String stubs (T-984)

D-229 makes BuildingPropertyTag the typed step-3 output that replaces the era/
society_profile/zone_palette String stubs on the skeleton. The tag + its derivation
(zone_type_id, flavor_ref, era/ConstructionEra, FloorExtent) all landed under T-957/
T-1006; this removes the now-dead stub fields they superseded:

- BlockSkeleton.era_modifications: Vec<EraModification> (era is per-footprint on
  BuildingPropertyTag.era now; era_cause retained as the block-level cause)
- QuarterSkeleton.society_profile: SocietyProfileRef (culture → tag.flavor_ref)
- QuarterSkeleton.zone_palette: Vec<ZoneDefinition> (zoning → tag.zone_type_id;
  distinct from FloorZone.zone_palette: ZonePalette, the real D-101 palette, kept)
- the now-orphaned `EraModification` and `SocietyProfileRef` String aliases

Kept: chunk_layout (real ChunkLayout / D-234 street network), z_band_zones (still
uses the ZoneDefinition alias), boundaries (separate stub, not D-229 scope).

cargo check + clippy -D warnings --all-targets clean; full server lib suite
1325 passed / 0 failed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/src/simulation/generator.rs

@@ -46,16 +46,12 @@ pub type WaterType = String;
 pub type SpecializedFunction = String;
 /// Cultural / architectural era tag. Stub.
 pub type Era = String;
-/// Single era modification applied to a block (conversion, overlay, hybrid). Stub.
-pub type EraModification = String;
 /// Landmark slot description within a block. Stub.
 pub type LandmarkSlot = String;
 // `ChunkLayout`, `CorridorSpine`, `AccessPoint` are typed street-network structs
 // (D-234, #957) — see the "Street-network types" section below.
 /// District context — neighboring districts, world position, system. Stub.
 pub type QuarterContext = String;
-/// Society profile reference (Miri's cultural ingredients). Stub.
-pub type SocietyProfileRef = String;
 /// Zone definition — base palette + modifiers + zone name. Stub.
 pub type ZoneDefinition = String;
 /// District boundary system — edge descriptors with neighbors. Stub.
@@ -1104,9 +1100,9 @@ pub struct BlockSkeleton {
     pub reservation: Option<ReservationId>,
     pub chunk_layout: ChunkLayout,
     pub hosted_sites: Vec<SocialSiteId>,
-    // Per-block `era: Era` (String stub) removed in #957 — construction era now
-    // lives per-footprint on `BuildingPropertyTag.era` (typed `ConstructionEra`).
-    pub era_modifications: Vec<EraModification>,
+    // Per-block `era: Era` / `era_modifications` String stubs removed (#957, T-984) —
+    // construction era now lives per-footprint on `BuildingPropertyTag.era` (typed
+    // `ConstructionEra`); `era_cause` is retained as the block-level cause.
     pub era_cause: Option<EraCause>,
     /// Build density percentage (0 = open/empty, 100 = fully built-up).
     /// Integer to avoid f32 non-determinism (D-010).
@@ -1298,9 +1294,9 @@ pub struct QuarterSkeleton {
     pub social_sites: Vec<SocialSitePlacement>,
     pub access_points: Vec<AccessPoint>,
 
-    // ── Cultural / World Context ──────────────────────────
-    pub society_profile: SocietyProfileRef,
-    pub zone_palette: Vec<ZoneDefinition>,
+    // Cultural / zone String stubs (`society_profile`, `zone_palette`) removed
+    // (T-984, D-229) — per-building culture and zoning now live on
+    // `BuildingPropertyTag` (`flavor_ref`, `zone_type_id`) in the district's `block_tags`.
 
     // ── Boundary System ───────────────────────────────────
     pub boundaries: QuarterBoundaries,