feat(simulation): complete interaction and monologue pipelines (#413, #414, #415)

Three fixes to make the gameplay loop functional end-to-end:

- Add Interactable component to NPC spawn so E-prompt detection works
- Build monologue trigger system (enter_location + time_idle) with
  MonologueBuffer/MonologueState components, wire through ObserverSnapshot
  as current_monologue field, decode on client and display via HUD
- Change PlayerAction::Interact from unit to struct variant carrying
  optional target_entity_id and verb fields

Bumps protocol version from 4 to 5. Regenerates MessagePack fixtures.
All 200 tests pass (170 unit + 30 integration).

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

server/tests/game_loop.rs

@@ -8,6 +8,7 @@ use settled_reach_server::bridge::types::*;
 use settled_reach_server::bridge::{BridgePlugin, BridgeResource};
 use settled_reach_server::knowledge::{KnowledgeGraph, KnowledgePlugin};
 use settled_reach_server::simulation::interaction::NearbyInteractionBuffer;
+use settled_reach_server::simulation::monologue::{MonologueBuffer, MonologueState};
 use settled_reach_server::simulation::movement::{PlayerCharacter, TilePosition, WalkabilityMap};
 use settled_reach_server::simulation::SimulationPlugin;
 use std::io::{BufReader, BufWriter};
@@ -36,6 +37,8 @@ fn player_moves_north_through_full_pipeline() {
             TilePosition::new(16, 16, 0),
             KnowledgeGraph::new(),
             NearbyInteractionBuffer::default(),
+            MonologueBuffer::default(),
+            MonologueState::default(),
         ));
 
         // Run one tick: receive input, process, validate movement, generate snapshot, send
@@ -63,7 +66,7 @@ fn player_moves_north_through_full_pipeline() {
         rmp_serde::from_slice(&response).expect("deserialize snapshot");
 
     // Snapshot captures state at end of tick 0 (before advance_tick increments to 1)
-    assert_eq!(snapshot.version, 4);
+    assert_eq!(snapshot.version, 5);
     assert_eq!(snapshot.tick, 0);
     assert_eq!(snapshot.entities.len(), 1);