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/operations/scripts/switch_wecom_bot.py

@@ -4,6 +4,7 @@ import sys
 
 from svc.config.paths import db_path
 from svc.persistence.sqlite_store import SqliteStore
+from svc.persistence.assistant_store import get_assistant_store
 
 
 _CLEAR_KEYS = [
@@ -29,7 +30,7 @@ def main() -> int:
         print("error=missing_required_args")
         return 2
 
-    store = SqliteStore(db_path())
+    store = get_assistant_store()
     store.set_setting("wecom_mode", "bot_api")
     store.set_setting("wecom_bot_id", bot_id)
     store.set_secret("wecom_bot_secret", bot_secret)