Fixes all integration CI failures on the 2.0 branch.
## What was broken
Two independent root causes:
1. **202 assertion failures** -- Under 4-fork CI parallel load, the 30s
`SYNC_WAIT_MS` sync window can expire before a BullMQ worker finishes a
heavy encode (avif, heic), returning a legitimate `202 {jobId, async: true}`
instead of `200`. Tests that hard-asserted `200` were spuriously failing.
2. **Vitest timeout race** -- `SYNC_WAIT_MS` (30s) and the default Vitest
`testTimeout` (also 30s) fired simultaneously. Vitest won the race,
reporting "Test timed out in 30000ms" instead of the test receiving the
202 response.
## Fixes
- Added `isAsyncFallback()` helper to four integration test files; validates
the `{async: true, jobId}` body shape and returns early so the synchronous
200 path runs full assertions only when warranted.
- Set `vi.setConfig({ testTimeout: 60_000 })` at module level in
`image-enhancement.test.ts` and `format-matrix-comprehensive.test.ts`,
giving a 30s buffer between when `waitForJob()` returns 202 and when
Vitest gives up.
- Bumped explicit matrix timeouts in `format-matrix.test.ts` and
`new-formats.test.ts` from 30s to 60s for the same reason.
- Installed missing CI doc-engine binaries (qpdf, pandoc, libreoffice,
pdfcpu) that were causing unrelated integration failures.
- Fixed E2E smoke specs for 2.0 UI changes (modality selector, tool routes,
validation behavior).
AVIF encoding is slow in CI without hardware acceleration, causing
SVG->AVIF and WebP->AVIF tests to timeout at 30s. Set 120s timeout
for all AVIF output tests, matching the existing exotic format timeout.
