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/test/tests/test_world.gd

@@ -0,0 +1,34 @@
+extends RefCounted
+## Headless tests for the procedural world and navigation mesh.
+
+const WorldBuilder := preload("res://src/game/world_builder.gd")
+
+func test_navmesh_built() -> bool:
+	var root := Node3D.new()
+	WorldBuilder.new(root).build()
+	var region: NavigationRegion3D = root.find_child("NavRegion", true, false) as NavigationRegion3D
+	if region == null:
+		return TestUtils.fail("no NavRegion in world")
+	var mesh: NavigationMesh = region.navigation_mesh
+	if mesh == null:
+		return TestUtils.fail("NavRegion has no navigation mesh")
+	var a := TestUtils.check(mesh.get_polygon_count() > 0, "navmesh has polygons")
+	var b := TestUtils.check(mesh.get_vertices().size() >= 4, "navmesh has vertices")
+	root.free()
+	return a and b
+
+func test_door_indicator_built() -> bool:
+	var root := Node3D.new()
+	var builder := WorldBuilder.new(root)
+	builder.build()
+	var a := TestUtils.check(builder.door_indicator != null, "door indicator mesh exists")
+	if builder.door_indicator != null:
+		builder.set_door_locked(true)
+		var mat: StandardMaterial3D = builder.door_indicator.material_override as StandardMaterial3D
+		var b := TestUtils.check(mat != null and mat.albedo_color.r > 0.5, "indicator turns red when locked")
+		builder.set_door_locked(false)
+		var c := TestUtils.check(mat != null and mat.albedo_color.g > 0.5, "indicator turns green when open")
+		root.free()
+		return a and b and c
+	root.free()
+	return a