feat(04-02): extend prototype and matrix pending state

- add saved session and last token tracking in prototype state
- add matrix load/reset pending store helpers

sdk/prototype_state.py

@@ -31,6 +31,8 @@ class PrototypeStateStore:
     def __init__(self) -> None:
         self._users: dict[str, User] = {}
         self._settings: dict[str, dict[str, Any]] = {}
+        self._saved_sessions: dict[str, list[dict[str, str]]] = {}
+        self._last_tokens_used: dict[str, int] = {}
 
     async def get_or_create_user(
         self,
@@ -78,3 +80,16 @@ class PrototypeStateStore:
         elif action.action == "set_safety":
             safety = settings.setdefault("safety", DEFAULT_SAFETY.copy())
             safety[action.payload["trigger"]] = action.payload.get("enabled", True)
+
+    async def add_saved_session(self, user_id: str, name: str) -> None:
+        sessions = self._saved_sessions.setdefault(user_id, [])
+        sessions.append({"name": name, "created_at": datetime.now(UTC).isoformat()})
+
+    async def list_saved_sessions(self, user_id: str) -> list[dict[str, str]]:
+        return list(self._saved_sessions.get(user_id, []))
+
+    async def get_last_tokens_used(self, user_id: str) -> int:
+        return self._last_tokens_used.get(user_id, 0)
+
+    async def set_last_tokens_used(self, user_id: str, tokens: int) -> None:
+        self._last_tokens_used[user_id] = tokens