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/main.gd

@@ -173,6 +173,9 @@ func _process(delta: float) -> void:
 		_consume_conversation_ended()
 		_consume_dialogue_response()
 
+		# #554: Show save/load result notification
+		_consume_save_result()
+
 	# Track camera to player (D-015: locked, fixed-north).
 	# #117: Manual exponential smoothing — same pattern as EntityRenderer.LERP_SPEED.
 	# Teleport (flag set by _teleport_transition): snap immediately, resume lerp next frame.
@@ -381,6 +384,27 @@ func _consume_dialogue_response() -> void:
 	GameState.dialogue_response = null
 
 
+# #554: Show save/load result notification from server response.
+func _consume_save_result() -> void:
+	if GameState.save_result == null:
+		return
+	var result: Dictionary = GameState.save_result
+	GameState.save_result = null  # consume once
+	var msg: String
+	if result.get("success", false):
+		if result.get("kind", "") == "save":
+			msg = UIStrings.get_text("notifications.save_complete")
+		else:
+			msg = UIStrings.get_text("notifications.load_complete")
+	else:
+		if result.get("kind", "") == "save":
+			msg = UIStrings.get_text("notifications.save_failed")
+		else:
+			msg = UIStrings.get_text("notifications.load_failed")
+	if monologue_display:
+		monologue_display.show_notification(msg)
+
+
 # D-061: Handle dialogue option selection → send to server
 func _on_dialogue_option_selected(response_id: String, text: String) -> void:
 	SimBridge.send_input({