fix(simulation): address PR #37 review — doc corrections, race fix, marker cleanup

Hoshe review (4 items):
- types.rs: doc comment "Current: 6" → "Current: 9"
- dialogue.rs: walk-away doc duplicated numbering (items 4-5 were 2-3)
- test_world/mod.rs: comment "Reset plates at 49-51" → "49-55"
- content_scaling.rs: magic number 51 → constants::RESET_PLATE_STABLE_IDS.1

Tyre review (3 items):
- knowledge/types.rs: guard comments on decrement() floor at Hostile
- input.rs: TeleportToHub now clears ConfrontationDelivered marker
- content_scaling.rs: same magic number fix (covered above)

Additional:
- content_runtime.rs: barrier-based shutdown handshake fixes TCP RST
  race condition under parallel test execution
- dialogue_room.rs: clippy type_complexity allow on NPCS tuple array

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

server/src/bridge/types.rs

@@ -31,7 +31,7 @@ pub const PROTOCOL_VERSION: u8 = 9;
 /// Future fields: ambient sound events, HUD state (D-020 expansion).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ObserverSnapshot {
-    /// Protocol version for forward compatibility. Current: 6.
+    /// Protocol version for forward compatibility. Current: 9.
     pub version: u8,
     /// Simulation tick when this snapshot was produced
     pub tick: u64,