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>

svc/config/database.py

@@ -0,0 +1,57 @@
+"""Assistant database backend selection (SQLite default, PostgreSQL opt-in via env)."""
+
+from __future__ import annotations
+
+import os
+
+
+def assistant_db_backend() -> str:
+    """Return ``sqlite`` (default) or ``postgresql``."""
+    raw = (
+        os.getenv("AIA_ASSISTANT_DB_BACKEND")
+        or os.getenv("OPS_ASSISTANT_DB_BACKEND")
+        or "sqlite"
+    ).strip().lower()
+    if raw in ("sqlite", ""):
+        return "sqlite"
+    if raw in ("pg", "postgres", "postgresql"):
+        return "postgresql"
+    raise ValueError(
+        f"Invalid assistant DB backend {raw!r}. "
+        "Use sqlite (default) or postgresql (aliases: pg, postgres)."
+    )
+
+
+def assistant_sqlalchemy_url() -> str:
+    """SQLAlchemy URL for the assistant store (sqlite or postgresql+psycopg)."""
+    if assistant_db_backend() == "postgresql":
+        raw = assistant_postgres_dsn()
+        if raw.startswith("postgresql+") or raw.startswith("postgres+"):
+            return raw
+        if raw.startswith("postgresql://") or raw.startswith("postgres://"):
+            return "postgresql+psycopg://" + raw.split("://", 1)[1]
+        return raw
+    from svc.config.paths import db_path
+
+    p = db_path().replace("\\", "/")
+    return f"sqlite+pysqlite:///{p}"
+
+
+def assistant_postgres_dsn() -> str:
+    """PostgreSQL connection URI for the assistant store (psycopg/libpq format)."""
+    url = (
+        os.getenv("AIA_ASSISTANT_DATABASE_URL")
+        or os.getenv("OPS_ASSISTANT_DATABASE_URL")
+        or os.getenv("AIA_ASSISTANT_PG_DSN")
+        or os.getenv("OPS_ASSISTANT_PG_DSN")
+        or ""
+    ).strip()
+    if not url:
+        raise ValueError(
+            "PostgreSQL backend requires AIA_ASSISTANT_DATABASE_URL (or OPS_ASSISTANT_DATABASE_URL) "
+            "to a libpq connection string, e.g. postgresql://user:pass@127.0.0.1:5432/oclaw"
+        )
+    return url
+
+
+__all__ = ["assistant_db_backend", "assistant_postgres_dsn", "assistant_sqlalchemy_url"]