feat(simulation): extend monologue event generation with new triggers (#119)

Add observe_npc, hear_sound, observe_anomaly, witness_interaction, and
post_conversation triggers to monologue system. trigger_event_monologue
system fires after sound collection, NPC conversations, and walk-away.
Context tags (location, situation, character_state) populated for D-035
content pool matching. COOLDOWN_TICKS=300 anti-spam guard respected.
witness_interaction fires after overheard NPC-to-NPC conversation per
D-078. Voice sounds and ambient sounds correctly excluded from
hear_sound trigger.

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

server/src/perception/interpretation.rs

@@ -68,6 +68,12 @@ impl ObservationEventQueue {
     pub fn is_empty(&self) -> bool {
         self.events.is_empty()
     }
+
+    /// Iterate over observation events without draining.
+    /// Used by monologue trigger system (#119) to react to previous-tick events.
+    pub fn iter(&self) -> impl Iterator<Item = &ObservationEvent> {
+        self.events.iter()
+    }
 }
 
 /// System: interpret visible snapshot against known routines and knowledge.