fix(server): address PR #23 review — 4 critical bugs, 3 warnings, 11 suggestions

Critical fixes:
- Add PendingRecognitionWire serialization roundtrip test
- Check Option return from delay.cancel() before logging
- InputQueue capacity limit (1000) with drop-oldest and warning
- TODO in observation.rs references ticket #450

Warning fixes:
- Hot-reload guards against invalid/empty content root
- Location header mismatch warning in line pool indexing
- walk_yaml() depth limit (100) against symlink loops
- Consecutive reload failure counter (warns after 5+)

Test additions:
- Negative prerequisite filtering test for monologue lines
- Integration test for pending_recognitions in observer snapshot
- Eavesdrop threshold ordering assertion (Careful < default)

Documentation:
- Playtesting expectation comments on delay constants
- is_pending() scalability note for future NPC cognitive delay
- ID format regex validation in line pool spec
- BTreeMap vs sort() ordering clarification in loader
- Multiplayer TODO in relationships.rs references D-010
- ContentSlug ticket #452 filed for entity slug resolution

394 tests, 0 failures.

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

server/src/perception/observation.rs

@@ -78,7 +78,7 @@ pub fn emit_observation_events(
         } else if let Some(ref mut delay) = cognitive_delay {
             // New entity + cognitive delay available: buffer recognition
             if !delay.is_pending(&stable_id) {
-                // TODO: wire RecognitionTrigger::Urgent for observe_anomaly triggers
+                // TODO(#450): wire RecognitionTrigger::Urgent for observe_anomaly triggers
                 let trigger = RecognitionTrigger::Normal;
                 delay.push(PendingRecognition {
                     target: entity,
@@ -135,8 +135,9 @@ pub fn emit_observation_events(
             delay.pending().iter().map(|p| p.stable_id).collect();
         for sid in pending_ids {
             if !visible_stable_ids.contains(&sid.0) {
-                delay.cancel(&sid);
-                tracing::debug!("Cognitive delay cancelled: stable_id={} left LOS", sid.0);
+                if delay.cancel(&sid).is_some() {
+                    tracing::debug!("Cognitive delay cancelled: stable_id={} left LOS", sid.0);
+                }
             }
         }
     }