feat(client): save/load client UI — F5/F6 quicksave/quickload (#554)

Wire SaveGame/LoadGame player actions through the full client stack:
protocol v15 decode, InputMapper F5/F6 bindings, SimBridge wire mapping
with one-shot carry-forward, GameState save_result field, and HUD
notification via monologue display. Quit-to-menu triggers quicksave
before scene change.

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

client/scripts/autoloads/input_mapper.gd

@@ -22,6 +22,8 @@ enum Action {
 	OPEN_JOURNAL,  # #264: J key — toggle knowledge journal panel, client-only
 	SET_FACING,  # D-054: facing octant update (no movement)
 	TELEPORT_HUB,  # #501: Home key — Gauntlet dev teleport (not production fast-travel)
+	SAVE_GAME,  # #554: F5 quicksave — sends SaveGame to server with save path
+	LOAD_GAME,  # #554: F6 quickload — sends LoadGame to server with save path
 }
 
 var input_queue: Array[Dictionary] = []
@@ -112,12 +114,23 @@ func _unhandled_input(event: InputEvent) -> void:
 	elif event.is_action_pressed("teleport_hub"):
 		if GameState.gauntlet_mode:
 			action = Action.TELEPORT_HUB
+	elif event.is_action_pressed("quicksave"):
+		action = Action.SAVE_GAME
+	elif event.is_action_pressed("quickload"):
+		action = Action.LOAD_GAME
 
 	if action != -1:
-		input_queue.append({
+		var entry := {
 			"action": action,
 			"timestamp_msec": Time.get_ticks_msec(),
-		})
+		}
+		# #554: Attach save path for SaveGame/LoadGame actions
+		if action == Action.SAVE_GAME or action == Action.LOAD_GAME:
+			var game_id := GameState.current_game_id
+			if game_id.is_empty():
+				return  # No active session — ignore save/load
+			entry["action_data"] = {"path": "user://saves/" + game_id + "/quicksave.sav"}
+		input_queue.append(entry)
 		get_viewport().set_input_as_handled()