feat(01-01): add matrix pending confirm store helpers

- add pending confirm prefix and storage helpers
- preserve existing matrix store behavior and tests

adapter/matrix/store.py

@@ -6,6 +6,7 @@ ROOM_META_PREFIX = "matrix_room:"
 USER_META_PREFIX = "matrix_user:"
 ROOM_STATE_PREFIX = "matrix_state:"
 SKILLS_MSG_PREFIX = "matrix_skills_msg:"
+PENDING_CONFIRM_PREFIX = "matrix_pending_confirm:"
 
 
 async def get_room_meta(store: StateStore, room_id: str) -> dict | None:
@@ -48,3 +49,15 @@ async def next_chat_id(store: StateStore, matrix_user_id: str) -> str:
     meta["next_chat_index"] = index + 1
     await set_user_meta(store, matrix_user_id, meta)
     return f"C{index}"
+
+
+async def get_pending_confirm(store: StateStore, room_id: str) -> dict | None:
+    return await store.get(f"{PENDING_CONFIRM_PREFIX}{room_id}")
+
+
+async def set_pending_confirm(store: StateStore, room_id: str, meta: dict) -> None:
+    await store.set(f"{PENDING_CONFIRM_PREFIX}{room_id}", meta)
+
+
+async def clear_pending_confirm(store: StateStore, room_id: str) -> None:
+    await store.delete(f"{PENDING_CONFIRM_PREFIX}{room_id}")