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),

server/src/bridge/types.rs

@@ -15,7 +15,7 @@ pub use crate::simulation::time::{DayPhase, TickRate};
 /// negotiation is unnecessary. Client should reject snapshots with version !=
 /// PROTOCOL_VERSION. New fields use #[serde(default)] only during the migration
 /// period, then the default is removed once both sides are updated.
-pub const PROTOCOL_VERSION: u8 = 4;
+pub const PROTOCOL_VERSION: u8 = 5;
 
 /// The ONLY data structure crossing the client-server boundary (D-020)
 /// Contains all information visible to the observer at a given tick.
@@ -23,8 +23,8 @@ pub const PROTOCOL_VERSION: u8 = 4;
 /// v2 adds: game_time, player_facing, visible_tiles, visibility sectors.
 /// v3 adds: relationship (D-033 entity color), observation (Visible/Remembered).
 /// v4 adds: nearby_interactions (D-060, #404 proximity + verbs[]).
-/// Future fields: ambient sound events, internal monologue triggers,
-/// HUD state (D-020 expansion).
+/// v5 adds: current_monologue (#414 internal monologue pipeline).
+/// Future fields: ambient sound events, HUD state (D-020 expansion).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ObserverSnapshot {
     /// Protocol version for forward compatibility. Current: 4.
@@ -42,6 +42,10 @@ pub struct ObserverSnapshot {
     /// Entities within interaction range with available verbs (D-060, #404).
     /// Sorted by distance (nearest first). v0.1 client reads verbs[0] on the nearest entity.
     pub nearby_interactions: Vec<NearbyInteraction>,
+    /// Internal monologue line to display this tick, if any (#414).
+    /// None when no monologue is triggered. Client shows text and auto-fades.
+    #[serde(default)]
+    pub current_monologue: Option<MonologueEvent>,
 }
 
 /// Game time data for client display (D-031)
@@ -159,7 +163,12 @@ pub enum PlayerAction {
     MoveNorthwest,
     MoveSoutheast,
     MoveSouthwest,
-    Interact,
+    /// Player pressed E on a nearby entity. Carries target + verb from client.
+    /// v0.1: logged only — full dialogue dispatch is future scope (#415).
+    Interact {
+        target_entity_id: Option<u64>,
+        verb: Option<String>,
+    },
     UsePerceptionMode(String),
     Pause,
     Unpause,
@@ -204,6 +213,18 @@ pub enum VerbKind {
     Talk,
 }
 
+/// Internal monologue event sent to the client for display (#414).
+/// Contains the text and display duration. Client auto-fades after duration.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct MonologueEvent {
+    /// Monologue line ID (for dedup and cooldown tracking)
+    pub id: String,
+    /// The monologue text to display
+    pub text: String,
+    /// Display duration in seconds before fade
+    pub duration_seconds: f32,
+}
+
 /// Snapshot buffer resource for staging outgoing ObserverSnapshots
 #[derive(Resource, Debug, Default)]
 pub struct SnapshotBuffer {