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>

client/scripts/autoloads/game_state.gd

@@ -22,6 +22,9 @@ var player_entity_id: int = 1
 # v4 fields (#404/#405)
 var nearby_interactions: Array = []  # [{entity_id, entity_type, distance, verbs: [{kind, label, priority, available}]}]
 
+# v5 fields (#414)
+var current_monologue: Variant = null  # {id, text, duration_seconds} or null
+
 func apply_snapshot(snapshot: Dictionary) -> void:
 	current_snapshot = snapshot
 
@@ -73,6 +76,12 @@ func apply_snapshot(snapshot: Dictionary) -> void:
 	else:
 		nearby_interactions = []
 
+	# v5: current_monologue (#414)
+	if snapshot.has("current_monologue") and snapshot.current_monologue is Dictionary:
+		current_monologue = snapshot.current_monologue
+	else:
+		current_monologue = null
+
 	# v2: visible_tiles with visibility sectors
 	# Derives visible_positions when not explicitly provided (real server mode)
 	if snapshot.has("visible_tiles") and snapshot.visible_tiles is Array and snapshot.visible_tiles.size() > 0:

client/scripts/autoloads/sim_bridge.gd

@@ -309,6 +309,15 @@ func _test_snapshot() -> Dictionary:
 			],
 		})
 
+	# v5: monologue on first tick (#414)
+	var monologue: Variant = null
+	if _test_tick == 1:
+		monologue = {
+			"id": "test_enter_001",
+			"text": "Sova Transit District. Population twelve thousand and change.",
+			"duration_seconds": 5.0,
+		}
+
 	return {
 		"tick": _test_tick,
 		"version": Protocol.PROTOCOL_VERSION,
@@ -324,6 +333,7 @@ func _test_snapshot() -> Dictionary:
 		"visible_tiles": _test_visible_tiles(),
 		"visible_positions": _test_visible_positions(),
 		"nearby_interactions": nearby,
+		"current_monologue": monologue,
 	}
 
 # Generate a small test room: 8x6 room with walls, a door, and floor

client/scripts/main.gd

@@ -22,6 +22,12 @@ func _process(_delta: float) -> void:
 		if world_renderer and world_renderer.has_method("update_from_state"):
 			world_renderer.update_from_state()
 
+		# Show monologue if server sent one this tick (#414)
+		if GameState.current_monologue != null and monologue_display:
+			var mono: Dictionary = GameState.current_monologue
+			monologue_display.show_monologue(mono.get("text", ""), mono.get("duration_seconds", 5.0))
+			GameState.current_monologue = null  # Consume — don't re-show next frame
+
 	# Track camera to player position every frame (D-015: locked, no panning)
 	# Camera2D smoothing handles interpolation — we just set the target
 	camera.global_position = GameState.player_position * Constants.TILE_SIZE
@@ -31,9 +37,15 @@ func _process(_delta: float) -> void:
 	for input in inputs:
 		if input.action == InputMapper.Action.INTERACT:
 			var target_id: int = interaction_prompt.get_interaction_target()
+			# Always send struct form for Interact (#415) — server expects named fields
 			if target_id >= 0:
 				input["action_data"] = {
 					"target_entity_id": target_id,
 					"verb": interaction_prompt.get_selected_verb(),
 				}
+			else:
+				input["action_data"] = {
+					"target_entity_id": null,
+					"verb": null,
+				}
 		SimBridge.send_input(input)

client/scripts/protocol/protocol.gd

@@ -11,7 +11,7 @@ class_name Protocol
 
 ## Protocol version — must match server PROTOCOL_VERSION in bridge/types.rs.
 ## Reject snapshots where version != this value.
-const PROTOCOL_VERSION: int = 4
+const PROTOCOL_VERSION: int = 5
 
 
 # -- Decode: bytes from server → GDScript types --------------------------------
@@ -94,6 +94,16 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 			if ni != null:
 				nearby_interactions.append(ni)
 
+	# v5: current_monologue (#414)
+	var current_monologue: Variant = null
+	var raw_monologue: Variant = raw.get("current_monologue")
+	if raw_monologue is Dictionary and raw_monologue.has("text"):
+		current_monologue = {
+			"id": str(raw_monologue.get("id", "")),
+			"text": str(raw_monologue["text"]),
+			"duration_seconds": float(raw_monologue.get("duration_seconds", 5.0)),
+		}
+
 	return {
 		"tick": tick,
 		"entities": entities,
@@ -103,6 +113,7 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 		"player_facing": player_facing,
 		"visible_tiles": visible_tiles,
 		"nearby_interactions": nearby_interactions,
+		"current_monologue": current_monologue,
 	}