Regression test from PR #106365 (one of its two tests kept: the full peer-dm
e2e; the listing-shape test asserted the same row and was dropped). The
handler-level fallback that shipped with the test is replaced by a SessionDB
fix in the follow-up commit, so this commit carries only the test.
Bot Mode always hides canonical 'Bot Chat' sessions, but _find_bot_chat's
GET /api/sessions listing used the default include_hidden=False path, so
the existing hidden row was invisible, _ensure_bot_chat tried to create a
duplicate, and the peer DB's UNIQUE(title) guard rejected it — DM failed.
- api_server: GET /api/sessions now accepts an exact-title lookup
(?title=...) and honors include_hidden=1 ONLY alongside a title filter,
so canonical hidden rows resolve without exposing a blanket hidden
listing on the client surface. The title needle is pushed into SQL
(search_query) so old hidden rows outside the recency window are found.
- peer dm client: _find_bot_chat sends title + include_hidden=1; older
peers ignore the unknown params and degrade to today's behavior.
- Clear diagnosable error on the older-peer duplicate-create rejection,
naming the hidden canonical chat and the PATCH hidden:false workaround.
- Unit tests (hidden resolution, no duplicate create, older-peer error,
older-peer visible fallback) + real-gateway E2E over a real state.db.
Root-cause analysis and regression recipe by @kubaboski in #91583.
Fixes#91583
finn763