- Enable `unicorn/better-dom-traversing` and switch the flagged
`.children[0]` / `.childNodes[0]` accesses to `.firstElementChild` /
`.firstChild`.
- Remove the obsolete `eslint-plugin-no-use-extend-native` type stub; it is
no longer a dependency.
- Drop misleading comments on `no-thenable` (enabled here, not disabled) and
`try-complexity`.
Assisted-by: claude-code:opus-4.8
Update eslint and all plugins. Many plugins still do not ship type
definitions so I had to add stubs. Also, I had to put a few typescript
error expectations because if some unknown error in the types.
`eslint-plugin-no-jquery` is disabled because it's not compatible with
eslint 9 flat config
(https://github.com/wikimedia/eslint-plugin-no-jquery/issues/311).
1. Enable
[strictFunctionTypes](https://www.typescriptlang.org/tsconfig/#strictFunctionTypes)
2. Introduce `DOMEvent` helper type which sets `e.target`. Surely not
totally correct with that `Partial` but seems to work.
3. Various type-related refactors, change objects in
`eventsource.sharedworker.ts` to `Map`.
