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/input_mapper.gd

@@ -0,0 +1,58 @@
+extends Node
+
+# Semantic actions — NO raw key codes cross the bridge
+enum Action {
+	MOVE_NORTH, MOVE_SOUTH, MOVE_EAST, MOVE_WEST,
+	INTERACT, USE_PERCEPTION_MODE, OPEN_MENU, PAUSE
+}
+
+var input_queue: Array[Dictionary] = []
+
+func _unhandled_input(event: InputEvent) -> void:
+	# Only process key press events (not releases or repeats)
+	if not event is InputEventKey:
+		return
+	if not event.pressed or event.echo:
+		return
+
+	var action: Action = -1
+	var action_name: String = ""
+
+	# Map input actions to semantic Action enum
+	if event.is_action_pressed("move_north"):
+		action = Action.MOVE_NORTH
+		action_name = "move_north"
+	elif event.is_action_pressed("move_south"):
+		action = Action.MOVE_SOUTH
+		action_name = "move_south"
+	elif event.is_action_pressed("move_east"):
+		action = Action.MOVE_EAST
+		action_name = "move_east"
+	elif event.is_action_pressed("move_west"):
+		action = Action.MOVE_WEST
+		action_name = "move_west"
+	elif event.is_action_pressed("interact"):
+		action = Action.INTERACT
+		action_name = "interact"
+	elif event.is_action_pressed("perception_mode"):
+		action = Action.USE_PERCEPTION_MODE
+		action_name = "perception_mode"
+	elif event.is_action_pressed("open_menu"):
+		action = Action.OPEN_MENU
+		action_name = "open_menu"
+	elif event.is_action_pressed("pause"):
+		action = Action.PAUSE
+		action_name = "pause"
+
+	# Queue the action if valid
+	if action != -1:
+		input_queue.append({
+			"action": action,
+			"timestamp_msec": Time.get_ticks_msec()
+		})
+		get_viewport().set_input_as_handled()
+
+func flush_queue() -> Array[Dictionary]:
+	var queue = input_queue.duplicate()
+	input_queue.clear()
+	return queue