feat(client): protocol v6 bridge — stance, inventory, input mapping

Upgrade client protocol bridge from v5 to v6 to match server.
Adds player_stance (4 variants) and player_inventory decode to
ObserverSnapshot. Adds TOGGLE_STANCE_UP/DOWN to InputMapper.
Includes 25 gdUnit4 tests for v6 decode + server serialization
test gap fix.

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

client/scripts/autoloads/game_state.gd

@@ -25,6 +25,10 @@ var nearby_interactions: Array = []  # [{entity_id, entity_type, distance, verbs
 # v5 fields (#414)
 var current_monologue: Variant = null  # {id, text, duration_seconds} or null
 
+# v6 fields (#449, D-053, D-065)
+var player_stance: String = "Walk"  # Sprint/Walk/Careful/Crouch
+var player_inventory: Array = []  # [{item_id, name, slot}]
+
 func apply_snapshot(snapshot: Dictionary) -> void:
 	current_snapshot = snapshot
 
@@ -82,6 +86,16 @@ func apply_snapshot(snapshot: Dictionary) -> void:
 	else:
 		current_monologue = null
 
+	# v6: player_stance (#449, D-053)
+	if snapshot.has("player_stance") and snapshot.player_stance is String:
+		player_stance = snapshot.player_stance
+
+	# v6: player_inventory (#449, D-065)
+	if snapshot.has("player_inventory") and snapshot.player_inventory is Array:
+		player_inventory = snapshot.player_inventory
+	else:
+		player_inventory = []
+
 	# 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/input_mapper.gd

@@ -6,7 +6,8 @@ extends Node
 enum Action {
 	MOVE_NORTH, MOVE_NORTHEAST, MOVE_EAST, MOVE_SOUTHEAST,
 	MOVE_SOUTH, MOVE_SOUTHWEST, MOVE_WEST, MOVE_NORTHWEST,
-	INTERACT, USE_PERCEPTION_MODE, OPEN_MENU, PAUSE
+	INTERACT, USE_PERCEPTION_MODE, OPEN_MENU, PAUSE,
+	TOGGLE_STANCE_UP, TOGGLE_STANCE_DOWN,
 }
 
 var input_queue: Array[Dictionary] = []
@@ -40,6 +41,10 @@ func _unhandled_input(event: InputEvent) -> void:
 		action = Action.OPEN_MENU
 	elif event.is_action_pressed("pause"):
 		action = Action.PAUSE
+	elif event.is_action_pressed("stance_up"):
+		action = Action.TOGGLE_STANCE_UP
+	elif event.is_action_pressed("stance_down"):
+		action = Action.TOGGLE_STANCE_DOWN
 
 	# Queue the action if valid
 	if action != -1:

client/scripts/autoloads/sim_bridge.gd

@@ -242,6 +242,8 @@ static func _action_enum_to_wire(action: int) -> String:
 		InputMapper.Action.INTERACT: return "Interact"
 		InputMapper.Action.USE_PERCEPTION_MODE: return "UsePerceptionMode"
 		InputMapper.Action.PAUSE: return "Pause"
+		InputMapper.Action.TOGGLE_STANCE_UP: return "ToggleStanceUp"
+		InputMapper.Action.TOGGLE_STANCE_DOWN: return "ToggleStanceDown"
 		InputMapper.Action.OPEN_MENU:
 			# Client-only action, not part of wire protocol
 			push_warning("SimBridge: OPEN_MENU is client-only, not sent to server")
@@ -328,6 +330,8 @@ func _test_snapshot() -> Dictionary:
 			"tick_rate": "Full",
 		},
 		"player_facing": _test_facing,
+		"player_stance": "Walk",
+		"player_inventory": [],
 		"entities": entities,
 		"tiles": _test_tiles(),
 		"visible_tiles": _test_visible_tiles(),