feat(simulation): sprint 16 dialogue server — response handler, trust gossip, variety tracker

Move dialogue system registrations from BridgePlugin to NpcPlugin (#538):
game logic that depends on NPC-layer resources now registers where it
belongs. BridgePlugin retains only wire protocol concerns.

Implement DialogueResponse verb handler (#539): new process_dialogue_response
system runs the full D-028 four-layer pipeline to select follow-up lines
when the player picks a dialogue option. Clears ActiveDialogue when no
candidates remain. Fix latent schedule ambiguity — emit_observation_events
now has explicit .before(advance_tick) constraint.

Verify trust-gated gossip pipeline (#171): confirmed process_talk_interaction
correctly passes KnowledgeConfidence through relationship_to_trust() per
D-075. Added integration tests for Secret-tier access (Friendly+KnowsDetails)
and Surface-only fallback (Friendly+Suspects).

Wire DialogueCooldownTracker into selection (#338): added regression test
confirming no line_id repeats within the 600-tick cooldown window across
10 consecutive Talk interactions.

Closes #538, #539, #171, #338

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

server/tests/serialization.rs

@@ -107,6 +107,10 @@ fn all_player_action_variants_roundtrip() {
         PlayerAction::ToggleStanceUp,
         PlayerAction::ToggleStanceDown,
         PlayerAction::WalkAway,
+        PlayerAction::DialogueResponse {
+            target_entity_id: 42,
+            response_id: "kael-davan_d_001".to_string(),
+        },
     ];
 
     for action in actions {