docs(simulation): finish district→quarter doc residue in gen_queue (#950)

PR #151 review (Hoshe/Tyre): four doc comments in gen_queue.rs still said
"district" next to the renamed quarter_id field / generate_quarter_skeleton.
Pure comment update, no code change.

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

server/src/atlas/gen_queue.rs

@@ -13,7 +13,7 @@
 //! **Work item types (D-206):**
 //! - `AnalyzeBody`:       D8 drainage + attractor extraction for a body.
 //! - `GenerateSkeleton`:  Phase 1 QuarterSkeleton for a city.
-//! - `FillChunk`:         Phase 2 chunk fill for a pre-loaded district.
+//! - `FillChunk`:         Phase 2 chunk fill for a pre-loaded quarter.
 //!
 //! Completion events are delivered to the main thread via
 //! `GenerationQueue::drain_completions()`, called once per tick from a Bevy
@@ -84,7 +84,7 @@ pub enum GenWorkItem {
     /// correct `BodyWorldState` cache entry (D-230).
     ///
     /// `quarter_id` is the stable content-addressable id for the generated
-    /// district (keyed by city position + world seed).
+    /// quarter (keyed by city position + world seed).
     ///
     /// `economic_role`, `population`, and `founding_age_years` are D-199 fields
     /// carried alongside the context because `generate_quarter_skeleton` accepts them as
@@ -94,16 +94,16 @@ pub enum GenWorkItem {
         body_id: String,
         /// D-199 economic read-set + all other context fields.
         context: Box<CityGenerationContext>,
-        /// Stable content-addressable district id (D-194/D-230).
+        /// Stable content-addressable quarter id (D-194/D-230).
         quarter_id: u64,
-        /// District-level seed chain (D-224).
+        /// Quarter-level seed chain (D-224).
         chain: SeedChain,
         // 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.
+    /// Pre-fill a chunk in an existing quarter.
     FillChunk {
         quarter_id: u64,
         block_pos: (u32, u32),