google_photos: starting on the connect page creates two picker sessions

[bdbarnett]

On a fresh start with no picks (start_page=connect), the log prints "open this link in Google Photos" twice, with two different session links. That's the same on Windows CPython and Linux CPython, in real mode. The QR code shows the second session and the first one is orphaned. Google expires it, so nothing breaks, but each start makes one extra API call and leaves a dangling session.

It isn't the double-start guard: _LAUNCHER_OWNS_RUN holds. The likely cause is the screen build at gphotos_lvgl.py ~437, which calls _start_pick(rebuild=False) whenever page == "connect". If that build runs twice at startup (a rescale, or a re-layout), each run starts a session. The fix is to start a session only when none is pending. Found 2026-09-23 during the first real run.

[bdbarnett]

Not a bug in the count: it's one session per start. With a mocked engine, create_session() ran once on a fresh start, once on a start with a leftover session in prefs, once per PICK and once per New link. Against the real API it was one POST /sessions on each of two consecutive starts. The "second link" was the previous run's session: restore() loaded it from prefs, and the connect page drew and printed it before the new session arrived. Since #144 the page waits for the new session instead of showing the old one, and the link is printed once, when a new session is created.