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

eslint/use-typed-gates.js

@@ -1,31 +1,41 @@
 'use strict'
 
-exports.create = function create(context) {
-  return {
-    ImportSpecifier(node) {
-      if (
-        !node.local ||
-        node.local.type !== 'Identifier' ||
-        node.local.name !== 'useGate'
-      ) {
-        return
-      }
-      if (
-        node.parent.type !== 'ImportDeclaration' ||
-        !node.parent.source ||
-        node.parent.source.type !== 'Literal'
-      ) {
-        return
-      }
-      const source = node.parent.source.value
-      if (source.startsWith('statsig') || source.startsWith('@statsig')) {
-        context.report({
-          node,
-          message:
-            "Use useGate() from '#/lib/statsig/statsig' instead of the one on npm.",
-        })
-      }
-      // TODO: Verify gate() call results aren't stored in variables.
+module.exports = {
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description:
+        'Enforce using internal statsig wrapper instead of npm package',
     },
-  }
+    schema: [],
+  },
+  create(context) {
+    return {
+      ImportSpecifier(node) {
+        if (
+          !node.local ||
+          node.local.type !== 'Identifier' ||
+          node.local.name !== 'useGate'
+        ) {
+          return
+        }
+        if (
+          node.parent.type !== 'ImportDeclaration' ||
+          !node.parent.source ||
+          node.parent.source.type !== 'Literal'
+        ) {
+          return
+        }
+        const source = node.parent.source.value
+        if (source.startsWith('statsig') || source.startsWith('@statsig')) {
+          context.report({
+            node,
+            message:
+              "Use useGate() from '#/lib/statsig/statsig' instead of the one on npm.",
+          })
+        }
+        // TODO: Verify gate() call results aren't stored in variables.
+      },
+    }
+  },
 }