The layout is load-bearing for review: re-dumping a locale with a different
`indent` rewrites every line, so the diff hides the actual change. Assert that each
file still matches the canonical serialisation it is maintained in (`en.json`
indent=2, the translated locales indent=4, `ensure_ascii=False`, one trailing
newline), so the mistake fails in CI instead of in review.
Fix ~790 basedpyright errors across the test suite:
- Type stub subclasses of real production classes with super().__init__()
- Add missing generic type arguments and Dict[str, Any] annotations
- Add None guards before subscript/member access
- Adapt tests to production API changes (removed dead handlers,
PersistentModelCache.get_default, _i18n_filter_added location)
Will Miao