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>

interfaces/gateway/http_adapter.py

@@ -2,15 +2,14 @@ from __future__ import annotations
 
 from typing import Any
 
-from svc.config.paths import db_path
-from svc.persistence.sqlite_store import SqliteStore
+from svc.persistence.assistant_store import get_assistant_store
 
 from .context_builder import build_common_gateway_context
 from .dispatcher import build_gateway_method_handlers
 
 
 def _build_http_context() -> dict[str, Any]:
-    store = SqliteStore(db_path())
+    store = get_assistant_store()
     context = build_common_gateway_context(store=store)
     context["session_event_subscribers"] = set()
     context["session_message_subscribers"] = {}