docs(ai): queue data-testid hardening + reflect PR #152 + 3-runner setup

TODO.md: Promote pytest-xdist to ✅ (PR #151 carries it). Adds three new
backlog items:
- data-testid hardening for e2e-critical interactive elements (sparked
  by PR #152's selector drift work)
- per-test transactional rollback (next big speedup if needed)
- pytest-testmon for PR-time test selection

HANDOFF.md: Three open PRs now (#150, #151, #152), all independent.
Three Gitea runner agents now registered, so jobs run in parallel.
Combined with #151's xdist, the prior 1h 14m wall-clock should drop
to ~6-10 min. Updated merge order: #152 first (smallest), #150 next,
#151 last. After all three land, enable CI / backend then CI / e2e
as required status checks.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.ai/TODO.md

@@ -5,9 +5,12 @@
 
 ## Up next
 
-- [ ] **Parallelize backend pytest with pytest-xdist.** Currently the backend suite takes ~22 min wall-clock for `1076 passed, 35 deselected` (verified locally 2026-04-25). With `-n auto` on the homelab Gitea Actions runner, this should land in the 3–6 min range depending on core count. Blocker: `test_db` fixture in `backend/tests/conftest.py` does `DROP SCHEMA public CASCADE` per test, which two workers would race on. Standard fix: one database per worker, derived from `PYTEST_XDIST_WORKER` env var inside conftest. The runner has spare CPU, so prioritize once main is green and the 54-failure cleanup has landed.
+- [ ] **Parallelize backend pytest with pytest-xdist.** ✅ landing as PR #151. Verified locally: backend suite 22 min → 4m 28s with `-n auto` on the 8-core homelab runner. Per-worker DB isolation via `PYTEST_XDIST_WORKER` in conftest.py.
 
 ## Backlog
 
 - [ ] **Frontend lint warnings cleanup.** 23 `react-hooks/exhaustive-deps` warnings remain after PR #149 (mostly missing-deps in useEffect). Either fix them or audit them for known-safe ones and add eslint-disable comments. Not blocking CI today.
 - [ ] **Audit `filterwarnings` ignores added in `wip(handoff): restore backend suite to green`.** Codex added narrow `ResourceWarning` filters for unclosed socket/transport/event-loop noise from pytest-asyncio teardown. Worth periodically reviewing whether those are still needed (e.g. when bumping pytest-asyncio) — if a real warning appears in those forms it would be silenced.
+- [ ] **Add `data-testid` attributes to e2e-critical interactive elements.** PR #152 fixed five Playwright tests by chasing UI-text changes (`Sessions` → `Session History`, `Account Settings` → `Account Management`, `/assistant` → `/pilot`, "Flow Sessions" tab, Resume button on session cards). Each was a one-line selector update, but every UI churn re-breaks them. Adding stable `data-testid` attributes on the targeted elements (page heading wrappers, tab nav, primary action buttons) and switching tests to `getByTestId` would make these immune to copy/route renames. Scope it small — start with `SessionHistoryPage` heading, the AI/Flow Sessions tab buttons, the per-session `Resume` button, and the command-palette FlowPilot option.
+- [ ] **Per-test transactional rollback in `test_db` fixture.** Bigger engineering than xdist (which we already shipped). Instead of `DROP SCHEMA public CASCADE` per test, wrap each test in a savepoint and rollback at teardown. ~30-40% additional speedup on top of xdist for test-DB-heavy tests. Real refactor; only worth it if the suite gets significantly larger or runs more frequently.
+- [ ] **Consider `pytest-testmon` for PR-time test selection.** Tracks which tests touched which source files and only re-runs affected ones. Best for small PRs touching ~few files. Adds cache-invalidation complexity; only worth it if the suite stays painfully long even after xdist.