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/src/bridge/mod.rs

@@ -159,9 +159,12 @@ impl Plugin for BridgePlugin {
                         .after(crate::simulation::movement::validate_movement),
                     crate::simulation::interaction::compute_nearby_interactions
                         .after(crate::simulation::movement::validate_movement),
+                    crate::simulation::monologue::trigger_monologue
+                        .after(crate::simulation::movement::validate_movement),
                     crate::perception::observer::compute_observer_snapshot
                         .after(crate::perception::observer::compute_visibility_geometry)
                         .after(crate::simulation::interaction::compute_nearby_interactions)
+                        .after(crate::simulation::monologue::trigger_monologue)
                         .before(crate::simulation::time::advance_tick),
                     crate::perception::observation::emit_observation_events
                         .after(crate::perception::observer::compute_observer_snapshot),