feat(persistence): PostgreSQL assistant store, chat persist fixes, gateway scripts

- Add SQLAlchemy Core repos, pg adapter/compat, assistant_store factory, Alembic bootstrap and migration/cutover scripts.

- Harden chat_message writes (NUL scrub for PG), turn_uuid on attempt failure, WS turn_runner fallbacks and gateway executed_turn_uuid init.

- start_gateway: log paths, PS7 stderr handling via cmd, background stdout/stderr redirect; runtime assistant_runtime_log_dir export.

- Ops: clear_all_chat_sessions with PG-only --postgresql and env-gated wipe; clear_postgres_chat_sessions.ps1.

- Tests: SA repos, pg compat, persist fallback, smoke env isolation; CI and docs touch-ups.

Co-authored-by: Cursor <cursoragent@cursor.com>

runtime/hooks/bundled/session-memory/handler.py

@@ -7,6 +7,8 @@ import sys
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Tuple
 
+from svc.persistence.assistant_store import get_assistant_store
+
 
 HOOK_KEY = "session-memory"
 
@@ -125,7 +127,7 @@ def handle(event: Any) -> None:
         from svc.config.paths import db_path  # type: ignore
         from svc.persistence.sqlite_store import SqliteStore  # type: ignore
 
-        store = SqliteStore(db_path())
+        store = get_assistant_store()
         msgs = store.get_messages(session_id=session_id, limit=max_msgs_n)
     except Exception:
         msgs = []