Upgrade ESLint to v9 with flat config (#9680)

* Upgrade ESLint to v9 with flat config

- Upgrade eslint from v8 to v9.18.0
- Migrate from .eslintrc.js to eslint.config.mjs (flat config)
- Upgrade typescript-eslint to v8.20.0 (unified package)
- Replace eslint-plugin-import with eslint-plugin-import-x for flat config support
- Add globals package for environment globals
- Update eslint-plugin-bsky-internal with proper meta objects for ESLint v9
- Fix deprecated context.getScope() API usage
- Update bskyembed to use flat config
- Remove deprecated --ext flag from lint scripts
- Configure rules to maintain previous behavior while using new ESLint version

* Fix varsIgnorePattern to require character after underscore

Restore the original pattern `^_.+` instead of `^_` so that lingui's
`const { _ } = useLingui()` will still be flagged when unused.

* Update ESLint rule tests for flat config format

- Update RuleTester to use flat config languageOptions instead of
  eslintrc parser format
- Remove duplicate test case that ESLint v9 now detects
- Add Jest globals for test files

* update eslint package versions

* lint android a11y

* enable typechecked rules, switch them to warn

* fix yarn lock ci

* Fix CI failure

* Remove unused globals?

* Organize a bit, add quiet to main lint command

* Allow ternary

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Eric Bailey <git@esb.lol>

src/state/persisted/index.web.ts

@@ -22,6 +22,8 @@ const UPDATE_EVENT = 'BSKY_UPDATE'
 let _state: Schema = defaults
 const _emitter = new EventEmitter()
 
+// async, to match native implementation
+// eslint-disable-next-line @typescript-eslint/require-await
 export async function init() {
   broadcast.onmessage = onBroadcastMessage
   window.onstorage = onStorage
@@ -37,6 +39,7 @@ export function get<K extends keyof Schema>(key: K): Schema[K] {
 }
 get satisfies PersistedApi['get']
 
+// eslint-disable-next-line @typescript-eslint/require-await
 export async function write<K extends keyof Schema>(
   key: K,
   value: Schema[K],
@@ -82,6 +85,7 @@ export function onUpdate<K extends keyof Schema>(
 }
 onUpdate satisfies PersistedApi['onUpdate']
 
+// eslint-disable-next-line @typescript-eslint/require-await
 export async function clearStorage() {
   try {
     localStorage.removeItem(BSKY_STORAGE)
@@ -102,6 +106,7 @@ function onStorage() {
   }
 }
 
+// eslint-disable-next-line @typescript-eslint/require-await
 async function onBroadcastMessage({data}: MessageEvent) {
   if (
     typeof data === 'object' &&