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/atlas/gen_queue.rs

@@ -12,7 +12,7 @@
 //!
 //! **Work item types (D-206):**
 //! - `AnalyzeBody`:       D8 drainage + attractor extraction for a body.
-//! - `GenerateSkeleton`:  Phase 1 DistrictSkeleton for a city.
+//! - `GenerateSkeleton`:  Phase 1 QuarterSkeleton for a city.
 //! - `FillChunk`:         Phase 2 chunk fill for a pre-loaded district.
 //!
 //! Completion events are delivered to the main thread via
@@ -31,9 +31,9 @@ use crate::atlas::attractor_matching::CityRecord;
 use crate::atlas::body_world_state::BodyWorldState;
 use crate::atlas::cascade::{run_cascade_from_heightmap, CascadeLayer};
 use crate::atlas::heightmap::{load_heightmap_png, GRID_H, GRID_W};
-use crate::atlas::skeleton_gen::generate_skeleton;
+use crate::atlas::skeleton_gen::generate_quarter_skeleton;
 use crate::seed::SeedChain;
-use crate::simulation::generator::{CityGenerationContext, DistrictWorldState};
+use crate::simulation::generator::{CityGenerationContext, QuarterWorldState};
 
 // ---------------------------------------------------------------------------
 // Priority
@@ -73,7 +73,7 @@ pub enum GenWorkItem {
         /// (#955); empty if the body has no settlements (cascade stops at Layer 1).
         cities: Vec<CityRecord>,
     },
-    /// Generate a Phase 1 DistrictSkeleton for this city.
+    /// Generate a Phase 1 QuarterSkeleton for this city.
     ///
     /// `context` is the D-199 economic read-set pre-resolved at dispatch time.
     /// All 6 required fields must be populated before this item is submitted
@@ -83,11 +83,11 @@ pub enum GenWorkItem {
     /// `body_id` routes the resulting `SkeletonGenerated` completion into the
     /// correct `BodyWorldState` cache entry (D-230).
     ///
-    /// `district_id` is the stable content-addressable id for the generated
+    /// `quarter_id` is the stable content-addressable id for the generated
     /// district (keyed by city position + world seed).
     ///
     /// `economic_role`, `population`, and `founding_age_years` are D-199 fields
-    /// carried alongside the context because `generate_skeleton` accepts them as
+    /// carried alongside the context because `generate_quarter_skeleton` accepts them as
     /// separate parameters (its signature is not changed by this ticket).
     GenerateSkeleton {
         city_id: u64,
@@ -95,17 +95,17 @@ pub enum GenWorkItem {
         /// D-199 economic read-set + all other context fields.
         context: Box<CityGenerationContext>,
         /// Stable content-addressable district id (D-194/D-230).
-        district_id: u64,
+        quarter_id: u64,
         /// District-level seed chain (D-224).
         chain: SeedChain,
-        // D-199 raw fields passed to generate_skeleton separately.
+        // D-199 raw fields passed to generate_quarter_skeleton separately.
         economic_role: String,
         population: i64,
         founding_age_years: u32,
     },
     /// Pre-fill a chunk in an existing district.
     FillChunk {
-        district_id: u64,
+        quarter_id: u64,
         block_pos: (u32, u32),
     },
 }
@@ -135,14 +135,14 @@ pub enum GenCompletion {
     SkeletonGenerated {
         city_id: u64,
         /// The body this skeleton belongs to — used to route state into
-        /// `BodyWorldState.districts` (D-230).
+        /// `BodyWorldState.quarters` (D-230).
         body_id: String,
         /// District-level world state (skeleton + block tags) produced by the plan phase (D-230).
         /// Boxed to keep `GenCompletion` variant sizes balanced (D-230 skeleton is ~2.7 KB).
-        state: Box<DistrictWorldState>,
+        state: Box<QuarterWorldState>,
     },
     ChunkFilled {
-        district_id: u64,
+        quarter_id: u64,
         block_pos: (u32, u32),
     },
     /// Work item failed — body_id or city_id for logging.
@@ -385,7 +385,7 @@ fn run_work_item(item: &GenWorkItem) -> GenCompletion {
             city_id,
             body_id,
             context,
-            district_id,
+            quarter_id,
             chain,
             economic_role,
             population,
@@ -394,29 +394,29 @@ fn run_work_item(item: &GenWorkItem) -> GenCompletion {
             // Build the Phase 1 skeleton from the pre-resolved D-199 context.
             // `economic_role`, `population`, and `founding_age_years` are the
             // D-199 raw fields carried alongside the context because
-            // `generate_skeleton` accepts them as separate parameters.
-            let skeleton = generate_skeleton(
+            // `generate_quarter_skeleton` accepts them as separate parameters.
+            let skeleton = generate_quarter_skeleton(
                 context,
                 *population,
                 economic_role,
-                *district_id,
+                *quarter_id,
                 *founding_age_years,
                 *chain,
             );
             GenCompletion::SkeletonGenerated {
                 city_id: *city_id,
                 body_id: body_id.clone(),
-                state: Box::new(DistrictWorldState {
+                state: Box::new(QuarterWorldState {
                     skeleton,
                     block_tags: std::collections::BTreeMap::new(),
                 }),
             }
         }
         GenWorkItem::FillChunk {
-            district_id,
+            quarter_id,
             block_pos,
         } => GenCompletion::ChunkFilled {
-            district_id: *district_id,
+            quarter_id: *quarter_id,
             block_pos: *block_pos,
         },
     }
@@ -493,7 +493,7 @@ mod tests {
                 dominant_bulk_class: BulkClass::NonPhysical,
                 dominant_production_ubiquity: ProductionUbiquity::Common,
             }),
-            district_id: city_id * 10,
+            quarter_id: city_id * 10,
             chain: SeedChain::root(42 + city_id),
             economic_role: "service_mixed".to_string(),
             population: 500_000,
@@ -590,7 +590,7 @@ mod tests {
         let q = make_queue();
         q.submit(
             GenWorkItem::FillChunk {
-                district_id: 99,
+                quarter_id: 99,
                 block_pos: (0, 0),
             },
             GenPriority::High,