Reset Session

Drop the calling user's session-scoped state.

Wipes: - conversation buffer for session_id (if provided). - registered components under the user's FS sandbox.

The user id is sourced from the authenticated session — the session_id query parameter only addresses the conversation buffer entry and is never trusted for path resolution.

Returns a small envelope describing what was cleared, sufficient for ops/log correlation but stripped of anything sensitive:

{"status": "ok", "components_cleared": <int>, "session_id": <str|null>}