Rebased onto current main, where _ensure_session_db grew a per-profile
cache (get_hermes_home()-keyed) for /p/<profile>/ multiplex — after this
PR's base. The PR's async rewrite assumed the old single-self._session_db
model, so on current main `session_db=self._session_db` in _create_agent
would pass None in production (the real DB lives in the per-home cache).
Split the concern: keep a SYNC _ensure_session_db (per-profile, used by
_create_agent + the many sync-patching create_agent tests) and add an
async _ensure_session_db_async that captures the profile home on the loop
thread then offloads only the SQLite open via to_thread (single-flight).
Both share _open_and_cache_session_db. Request handlers use the async
variant; _create_agent reverts to the sync call. Updated the first-request
test's FakeDB to accept db_path to match main's SessionDB(db_path=...).
Co-authored-by: necoweb3 <sswdarius@gmail.com>
Brooklyn Nicholson
d2cb318509