feat(client): initialize Godot 4 project boilerplate (epic #277)

Set up the complete Godot 4.6 client foundation as a pure renderer (D-020):
- project.godot with 2D rendering, autoloads, input actions
- Main scene: Game > World (TileMapLayer, Entities, FogOverlay) + Camera2D + UILayer
- Autoloads: SimBridge (connection state machine + test mode), GameState, InputMapper
- Rendering stubs: WorldRenderer, EntityRenderer, FogRenderer
- UI stubs: HUD (health/perception/time), Minimap, MonologueDisplay
- Input mapping: WASD/arrows, E (interact), Tab (perception), Esc (menu), Space (pause)
- gdUnit4 smoke tests: scene loads, autoloads registered (2/2 passing)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/scripts/autoloads/game_state.gd

@@ -0,0 +1,28 @@
+extends Node
+
+# Updated each frame from ObserverSnapshot data
+var current_snapshot: Dictionary = {}
+var player_position: Vector2 = Vector2.ZERO
+var visible_entities: Array = []
+var fog_state: Dictionary = {}
+var hud_data: Dictionary = {}
+
+func apply_snapshot(snapshot: Dictionary) -> void:
+	current_snapshot = snapshot
+
+	# Parse player data
+	if snapshot.has("player") and snapshot.player.has("position"):
+		var pos = snapshot.player.position
+		player_position = Vector2(pos[0], pos[1])
+
+	# Parse entities
+	if snapshot.has("entities"):
+		visible_entities = snapshot.entities
+
+	# Parse fog state
+	if snapshot.has("fog"):
+		fog_state = snapshot.fog
+
+	# Parse HUD data
+	if snapshot.has("hud"):
+		hud_data = snapshot.hud