Implement TODO backlog: LATE phase fix, protester, CALL_SOMEONE, door lock, flashlight, persistence, navmesh, JSON localization, and release tooling

- Fix LATE shift phase (start 700s) so the violent-threat event is reachable
- Add PROTESTER archetype (rules, profile, colors, events in public venues)
- Add CALL_SOMEONE reaction (FSM -> ARGUING, influencer/trespasser/protester weights)
- Door lock: DoorState core class, L binding, red/green visual indicator,
  locked doors thwart FORCE_ENTRY
- Flashlight: G binding, SpotLight3D, perception radius bonus at evening/late
- Persistence: save shift results via Save autoload, history + best score on
  review screen, round-trip test
- Navigation: flat NavigationRegion3D navmesh, NavigationAgent3D path following
  with direct-movement fallback; steps made visual-only so NPCs reach entrance
- Localization: strings moved to content/strings.en.json (loader keeps
  lookup/fmt signatures; coverage test over all keys)
- Distribution: export_presets.cfg (Linux/Windows/macOS), tools/build_releases.sh,
  docs/RELEASING.md, prominent README Downloads section
- Remove stale signal_bus.gd (invalid static-signal experiment)
- Tests: 53 passing across 9 suites

src/game/npc_avatar.gd

@@ -12,6 +12,10 @@ var target_position: Vector3 = Vector3.ZERO
 var door_position: Vector3 = Vector3(0, 0.5, 1.2)
 var awaiting_interaction := false
 var arrived := false
+var agent: NavigationAgent3D = null
+## Set once the nav agent proves it has a path; direct movement is the fallback.
+var _nav_usable := false
+var _nav_try_frames := 0
 
 const TYPE_COLORS := {
 	Rules.NpcType.TOURIST: Color(0.90, 0.75, 0.55),
@@ -26,6 +30,7 @@ const TYPE_COLORS := {
 	Rules.NpcType.AUTHORIZED_GUEST: Color(0.60, 0.85, 0.65),
 	Rules.NpcType.DELIVERY: Color(0.80, 0.70, 0.40),
 	Rules.NpcType.RESPONDER: Color(0.25, 0.30, 0.85),
+	Rules.NpcType.PROTESTER: Color(0.90, 0.40, 0.20),
 }
 
 func _init() -> void:
@@ -42,6 +47,15 @@ func setup(profile: NpcProfile, intent: String, seed_value: int, p_spawn: Vector
 	position = p_spawn
 	npc.fsm.state_changed.connect(_on_state_changed)
 	_build_body(profile.npc_type)
+	_nav_usable = false
+	_nav_try_frames = 0
+	agent = NavigationAgent3D.new()
+	agent.name = "NavAgent"
+	agent.path_desired_distance = 0.4
+	agent.target_desired_distance = 4.0
+	agent.radius = 0.35
+	agent.height = 1.2
+	add_child(agent)
 
 	# Normalize intent targets: approach the entrance, stop near the door.
 	var collider := CollisionShape3D.new()
@@ -96,6 +110,40 @@ func _advance_fsm(delta: float) -> void:
 		awaiting_interaction = true
 
 func _move_toward_target(delta: float) -> void:
+	if agent == null:
+		_move_direct(delta)
+		return
+	agent.target_position = target_position
+	if agent.is_navigation_finished():
+		if (global_position - target_position).length() < 3.0:
+			_arrive()
+		else:
+			# Path finished but we are far away: navigation is unusable, fall back.
+			_move_direct(delta)
+		return
+	# Learn whether the navmesh actually serves this spot.
+	if not _nav_usable:
+		_nav_try_frames += 1
+		if agent.is_target_reachable():
+			_nav_usable = true
+		elif _nav_try_frames > 10:
+			_move_direct(delta)
+			return
+	var next := agent.get_next_path_position()
+	var dir := (next - global_position)
+	dir.y = 0.0
+	if dir.length() < 0.2:
+		velocity = Vector3.ZERO
+		return
+	dir = dir.normalized()
+	velocity.x = dir.x * 1.3
+	velocity.z = dir.z * 1.3
+	velocity.y -= 9.8 * delta
+	look_at(global_position + Vector3(dir.x, 0, dir.z), Vector3.UP)
+	move_and_slide()
+
+## Fallback used when no navigation mesh is available (e.g. minimal scenes).
+func _move_direct(delta: float) -> void:
 	var to_target := target_position - global_position
 	to_target.y = 0.0
 	var dist := to_target.length()