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/protocol/protocol.gd

@@ -11,7 +11,7 @@ class_name Protocol
 
 ## Protocol version — must match server PROTOCOL_VERSION in bridge/types.rs.
 ## Reject snapshots where version != this value.
-const PROTOCOL_VERSION: int = 14
+const PROTOCOL_VERSION: int = 15
 
 
 # -- Decode: bytes from server → GDScript types --------------------------------
@@ -233,6 +233,17 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 			"confidence": str(raw_examine.get("confidence", "KnowsOf")),
 		}
 
+	# v15: save_result (#554, D-085) — one-shot save/load operation result.
+	# {success: bool, kind: "save"|"load", error: String|null}
+	var save_result: Variant = null
+	var raw_save: Variant = raw.get("save_result")
+	if raw_save is Dictionary:
+		save_result = {
+			"success": bool(raw_save.get("success", false)),
+			"kind": str(raw_save.get("kind", "")),
+			"error": raw_save.get("error"),
+		}
+
 	# v14: player_knowledge (#264, D-041) — partial KG dump for journal panel.
 	# {entities: [{entity_id, name, confidence, source, state, relationship, last_observed_tick}],
 	#  facts: [{fact_id, confidence, source, state, acquired_tick}]}
@@ -290,6 +301,7 @@ static func decode_snapshot(bytes: PackedByteArray) -> Variant:
 		"poi_list": poi_list,
 		"examine_result": examine_result,
 		"player_knowledge": player_knowledge,
+		"save_result": save_result,
 	}
 
 

client/scripts/protocol/test_harness.gd

@@ -189,6 +189,7 @@ func snapshot() -> Dictionary:
 		"gauntlet_mode": gauntlet_mode,
 		"conversation_events": conv_events,
 		"conversation_ended": conv_ended,
+		"save_result": null,
 	}