## Linked issue
Closes#4863
## Summary / motivation
Adds Playwright as the e2e test framework so contributors can write
browser-based tests against a real headless Anki instance. There was no
automated way to exercise mediasrv pages, SvelteKit routes, or the
`/_anki/` RPC surface from a browser, this PR establishes that harness.
Key pieces:
- `qt/tests/launch_anki_for_e2e.py` — spawns a throwaway Anki instance
(temp `ANKI_BASE`, `QT_QPA_PLATFORM=offscreen`). Pre-seeds `prefs21.db`
so Anki skips the language picker and profile chooser and goes straight
to serving mediasrv.
- `playwright.config.ts` — points `webServer` at the launcher; polls
`/favicon.ico` as the readiness probe.
- `ts/tests/e2e/` — `fixtures.ts` base and a sanity spec that verifies
mediasrv is reachable and a SvelteKit page hydrates.
- `justfile` — `just test-e2e` recipe; Chromium installed to
`out/playwright-browsers/`.
- CI — e2e step in `check-linux`; failed-run artifacts uploaded for 7
days.
- `docs/e2e-testing.md` — contributor guide covering setup, managed vs
reuse-server modes, and writing new tests.
## How to test
Build the project once, then run the e2e suite in managed mode (no
separate `./run` needed — the launcher is started automatically):
```shell
just build
just test-e2e
```
## Before / after behavior (optional)
Before: no browser-level test harness existed.
After: `just test-e2e` drives a real headless Anki instance via
Playwright.
## Risk / compatibility / migration
No production code changed. New dev-only files and CI step only.
Chromium is installed to `out/playwright-browsers/` (gitignored) and
does not affect the regular build.
---------
Co-authored-by: Abdo <abdo@abdnh.net>
