ESPHome toolchain test gaps — venv runner argv, dashboard WS runner, rollout OOS skip, offline PyPI

FIXED 2026-09-06 (feat/esphome-completion): new brain/tests/test_esphome_toolchain.py, 26 tests — venv _run_job argv/cwd/PLATFORMIO_CORE_DIR, OTA –device –no-logs from inventory, hostless OTA fails clean, timeout kills; SEAT_YAML entries exist in firmware/v4; dashboard WebSocket runner (spawn payload, streamed lines, ‘too old’ hint); backend detection none / venv-host / dashboard-legacy / helper-missing; host-helper handshake success + failure; disk guard; downgrade refusal + rollback; PyPI offline (ok=false, no raise, fail cache); rollout OOS/hostless skip + prompt flag; default kit fleet order hub last; canary → rest; canary discarded when the toolchain moves; unknown mode; status shape on venv-host. Inventory is seeded by direct SQL because upsert_inventory syncs to the live hub (21 s connect timeout per call). Full suite 305 passed. Frontend: tsc + vite build (no vitest dep in the project; a render test was not added).