refactor(simulation): rename DistrictSkeleton→QuarterSkeleton per D-222 (#950)

D-222 renamed the 512m generation cell from District to Quarter (District
is now a new 2048m tier above it). Align the generation skeleton code to
the canonical vocabulary. Pure naming — no behavior change; all 1296 lib
tests + integration tests pass unchanged.

Renamed (spatial-cell identifiers):
- DistrictSkeleton → QuarterSkeleton, DistrictWorldState → QuarterWorldState
- DistrictId → QuarterId, DistrictContext/DistrictBoundaries → Quarter*
- field district_id → quarter_id, district_type → quarter_type
- BodyWorldState.districts map → .quarters
- generate_skeleton → generate_quarter_skeleton

Deliberately left as-is (these name functional ZONING, not the spatial
tier — orthogonal to D-222): DistrictType, DistrictLayoutMode, the
district_mix module (DistrictMix/compute_district_mix), and the
GenWorkItem::GenerateSkeleton / GenCompletion::SkeletonGenerated variants.

Also aligned the perception "sim tile" → "subtile" vocabulary (D-222:
Subtile = 0.5m) in decisions/perception.md and the generation-cascade code
comments. Historical D-066/D-094/D-201/D-220 decision bodies keep their
existing D-222 amendment notes (not rewritten in place); the public
max_offset_sim_tiles fn name is unchanged.

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

server/src/simulation/generator.rs

@@ -1,6 +1,6 @@
-//! World generator data model — district skeleton and mobile chunk types.
+//! World generator data model — quarter skeleton and mobile chunk types.
 //!
-//! Phase 1 generator output: the `DistrictSkeleton` produced by the world generation
+//! Phase 1 generator output: the `QuarterSkeleton` produced by the world generation
 //! pipeline. Consumed by Phase 2 (chunk fill) and by the simulation startup path.
 //!
 //! **D-110 (signed z-levels):** All z-level *position* fields use `i8` (negative values
@@ -24,7 +24,7 @@ use serde::{Deserialize, Serialize};
 // ---------------------------------------------------------------------------
 
 /// Unique district identifier (content-addressable via hash of world position + seed).
-pub type DistrictId = u64;
+pub type QuarterId = u64;
 /// Unique multi-block reservation identifier within a district.
 pub type ReservationId = u64;
 /// Unique social site identifier within a district.
@@ -55,13 +55,13 @@ pub type ChunkLayout = String;
 /// Corridor spine connecting district access points. Stub.
 pub type CorridorSpine = String;
 /// District context — neighboring districts, world position, system. Stub.
-pub type DistrictContext = String;
+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.
-pub type DistrictBoundaries = String;
+pub type QuarterBoundaries = String;
 /// Guarantee audit result — tier-appropriate spatial invariant checks. Stub.
 pub type GuaranteeAuditResult = String;
 /// District access point (entry/exit to neighboring district). Stub.
@@ -939,17 +939,17 @@ pub enum ProductionUbiquity {
     MonopolySource,
 }
 
-/// District-level world state produced by the plan phase (D-230).
+/// Quarter-level world state produced by the plan phase (D-230).
 ///
 /// Output of `GenerateSkeleton` extended to include building-property tags.
-/// Stored in `BodyWorldState.districts: BTreeMap<DistrictId, DistrictWorldState>`.
+/// Stored in `BodyWorldState.quarters: BTreeMap<QuarterId, QuarterWorldState>`.
 /// `BTreeMap` for D-010 determinism.
 ///
-/// D-230: `{ skeleton: DistrictSkeleton, block_tags: BTreeMap<(u8,u8), Vec<BuildingPropertyTag>> }`
+/// D-230: `{ skeleton: QuarterSkeleton, block_tags: BTreeMap<(u8,u8), Vec<BuildingPropertyTag>> }`
 #[derive(Serialize, Deserialize, Clone, Debug, Default, PartialEq)]
-pub struct DistrictWorldState {
+pub struct QuarterWorldState {
     /// Phase 1 skeleton produced by `GenerateSkeleton` (D-230).
-    pub skeleton: DistrictSkeleton,
+    pub skeleton: QuarterSkeleton,
     /// Building property tags keyed by block position (row, col) within the 4×4 grid.
     /// Each entry is a Vec of one tag per building footprint placed in that block.
     /// `BTreeMap` for D-010 determinism (no HashMap non-determinism).
@@ -999,7 +999,7 @@ pub struct CityGenerationContext {
 /// Organic layout placement for a single block.
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, Default)]
 pub struct BlockPlacement {
-    /// Offset from grid-aligned position (±16 sim tiles per axis max).
+    /// Offset from grid-aligned position (±16 subtiles per axis max).
     pub offset: (i16, i16),
     /// Rotation in 15° increments (0–3, max 45°).
     pub rotation_steps: u8,
@@ -1008,8 +1008,8 @@ pub struct BlockPlacement {
     pub street_width_bps: u16,
 }
 
-/// Single block within a district's 4×4 block grid.
-/// Each block = 128×128 sim tiles = 2×2 chunks.
+/// Single block within a quarter's 4×4 block grid.
+/// Each block = 128×128 subtiles = 2×2 chunks.
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Default)]
 pub struct BlockSkeleton {
     /// Grid position (0–3, 0–3).
@@ -1160,10 +1160,10 @@ pub struct MultiBlockReservation {
 }
 
 // ---------------------------------------------------------------------------
-// District skeleton
+// Quarter skeleton
 // ---------------------------------------------------------------------------
 
-/// Phase 1 generator output for one district.
+/// Phase 1 generator output for one quarter.
 ///
 /// Produced by the async background generation pipeline.
 /// Consumed by Phase 2 (chunk-by-chunk fill, on demand) and by
@@ -1171,8 +1171,8 @@ pub struct MultiBlockReservation {
 ///
 /// ## Z-level naming convention (D-110)
 ///
-/// - `z_levels: u8` — how many floor levels exist in this district (count, always ≥ 1)
-/// - `base_z` does not appear on `DistrictSkeleton` itself — the district's
+/// - `z_levels: u8` — how many floor levels exist in this quarter (count, always ≥ 1)
+/// - `base_z` does not appear on `QuarterSkeleton` itself — the quarter's
 ///   ground level is always 0. Sub-ground structures use [`MultiBlockReservation`]
 ///   with a negative `base_z` field.
 ///
@@ -1181,14 +1181,16 @@ pub struct MultiBlockReservation {
 /// All `Vec<_>` fields are stable-ordered at generation time (sorted by a
 /// deterministic key). Generation reproduces identical output for the same seed.
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Default)]
-pub struct DistrictSkeleton {
+pub struct QuarterSkeleton {
     // ── Identity ──────────────────────────────────────────
-    pub district_id: DistrictId,
+    pub quarter_id: QuarterId,
     /// Deterministic seed (derived from master seed via SeedChain).
     pub seed: u64,
-    pub district_type: DistrictType,
+    /// The quarter's primary functional zone (still a `DistrictType` — the
+    /// zoning vocabulary is orthogonal to the spatial tier, D-222).
+    pub quarter_type: DistrictType,
     /// World context (system, world, neighboring districts).
-    pub context: DistrictContext,
+    pub context: QuarterContext,
 
     // ── Classification ────────────────────────────────────
     pub world_tier: WorldTier,
@@ -1197,7 +1199,7 @@ pub struct DistrictSkeleton {
     pub layout_mode: DistrictLayoutMode,
 
     // ── Spatial Structure ─────────────────────────────────
-    /// The 4×4 block grid (each block = 128×128 sim tiles = 2×2 chunks).
+    /// The 4×4 block grid (each block = 128×128 subtiles = 2×2 chunks).
     pub blocks: [[BlockSkeleton; 4]; 4],
     /// Multi-block reservations (skyscrapers, parks, terminals, plazas).
     pub reservations: Vec<MultiBlockReservation>,
@@ -1215,7 +1217,7 @@ pub struct DistrictSkeleton {
     pub zone_palette: Vec<ZoneDefinition>,
 
     // ── Boundary System ───────────────────────────────────
-    pub boundaries: DistrictBoundaries,
+    pub boundaries: QuarterBoundaries,
 
     // ── Validation ────────────────────────────────────────
     /// Guarantee audit result. `None` for Empty districts.
@@ -1367,9 +1369,9 @@ mod tests {
         assert_eq!(r.z_levels, 30u8, "z_levels count must remain u8");
     }
 
-    /// D-110: z_levels (count) remains u8 on DistrictSkeleton.
+    /// D-110: z_levels (count) remains u8 on QuarterSkeleton.
     #[test]
-    fn district_skeleton_z_levels_is_unsigned() {
+    fn quarter_skeleton_z_levels_is_unsigned() {
         // Verify z_levels is u8 (cannot hold negative value). Static assertion:
         // if this compiled with z_levels = 255u8, the type is correct.
         fn assert_u8(_: u8) {}