fix(simulation): address PR #46 review — zone tests, doc accuracy, TBD comment

Add 3 zone enrichment tests to observer pipeline (tile inside zone,
tile outside zone, absent ZoneMap resource). Fix misleading Decay
Observatory doc comment that claimed Direct start when test starts at
KnowsDetails. Add production population TBD note on ZoneMap.

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

server/src/test_world/rooms/decay_observatory.rs

@@ -1,8 +1,9 @@
 //! Decay Observatory — Room 13 (24x14)
 //!
-//! Tests D-041 (knowledge graph decay). Observer starts with Direct confidence
-//! on an NPC in LOS, then LOS is broken. Tick advances verify confidence
-//! degrades: Direct → KnowsDetails → KnowsOf → Suspects → Stale (D-041).
+//! Tests D-041 (knowledge graph decay). Observer sees an NPC (Direct), then
+//! LOS is broken (drops to KnowsDetails). Tick advances verify confidence
+//! degrades: KnowsDetails → KnowsOf → Suspects (floor). Separate test
+//! confirms Stale state triggers when age exceeds stale_after threshold.
 //!
 //! Decay runs once per game-minute (every 10 ticks, D-031). Confidence floor
 //! is Suspects — decay never removes an entity from the knowledge graph.