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/runtime.py

@@ -23,6 +23,15 @@ def _runtime_log_dir() -> Path:
     return Path(db_path()).resolve().parent / "logs"
 
 
+def assistant_runtime_log_dir() -> Path:
+    """Directory for gateway/channel logs written by :func:`start_service`.
+
+    Same rule as ``AIA_RUNTIME_LOG_DIR`` or ``<parent of sqlite db_path>)/logs``.
+    Use this from shell scripts so paths match Python ``stack up`` / ``start_service``.
+    """
+    return _runtime_log_dir()
+
+
 def _read_state() -> dict[str, Any]:
     p = _runtime_file()
     if not p.exists():