fix(simulation): address PR #55 review — stale comment, range, duplication, docs

- Fix protocol version comment (12 → 13) in ObserverSnapshot doc
- Widen Want intensity range from 3..=9 to 1..=10 to match spec and test
- Replace duplicated pool selection in trigger_recognition_monologue with
  call to select_pool_line helper (~50 lines removed)
- Document NaiveSpatialIndex migration cost for grid/quadtree swap
- Remove misleading Default derive from TellCategory (Nervous is not a
  sensible default for neutral NPCs)
- Add caller invariant doc on generate_npc (no TilePosition spawned)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/bridge/types.rs

@@ -37,7 +37,7 @@ pub const PROTOCOL_VERSION: u8 = 13;
 /// Future fields: ambient sound events, HUD state (D-020 expansion).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ObserverSnapshot {
-    /// Protocol version for forward compatibility. Current: 12.
+    /// Protocol version for forward compatibility. Current: 13.
     pub version: u8,
     /// Simulation tick when this snapshot was produced
     pub tick: u64,