Remove package/** ignore from fast ESLint config after #644 resolution (#821)

## Summary

Removes the `package/**` ignore pattern from `eslint.config.fast.js` now
that issue #644 has been resolved. The fast config can now lint
TypeScript files alongside the main config.

## Changes

- **Removed**: `"package/**"` ignore pattern that was blocking all
TypeScript files
- **Added**: Specific ignores for generated files (`*.js`, `*.d.ts`)
matching main config
- **Added**: TypeScript-specific rule overrides matching main config
structure:
  - Global TypeScript rules (no-undef, no-require-imports)
  - File-specific overrides for config.ts, babel/preset.ts
- Module overrides for configExporter, utils, environments, plugins,
etc.
  - Type test overrides for intentionally unused variables
- **Added**: Global rules (no-console, no-restricted-syntax) for
consistency

## Verification

✅ Fast config now lints all TypeScript source files in `package/`
✅ Passes with 0 errors (verified with `ESLINT_USE_FLAT_CONFIG=true npx
eslint --config eslint.config.fast.js .`)
✅ Main config still passes (`yarn lint`)
✅ Provides faster feedback by skipping type-aware rules while
maintaining consistency

## Related Issues

- Closes #644 (referenced in TODO comment)
- Related to #783 (TypeScript ESLint technical debt tracking)

## Test Plan

- [x] Run `yarn lint` - passes with 0 errors
- [x] Run fast config directly - passes with 0 errors
- [x] Verify TypeScript files are linted in fast mode
- [x] Verify generated files (.js, .d.ts) are still ignored

🤖 Generated with [Claude Code](https://claude.com/claude-code)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Updated linting configuration to optimize build tooling and relax
certain code style rules for specific packages, improving development
workflow consistency.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: justin808

eslint.config.fast.js

@@ -17,11 +17,12 @@ module.exports = [
   // Global ignores (replaces .eslintignore)
   {
     ignores: [
-      "lib/**",
-      "**/node_modules/**",
-      "vendor/**",
-      "spec/**",
-      "package/**" // TODO: Remove after issue #644 is resolved (lints package/ TS source files)
+      "lib/**", // Ruby files, not JavaScript
+      "**/node_modules/**", // Third-party dependencies
+      "vendor/**", // Vendored dependencies
+      "spec/**", // Ruby specs, not JavaScript
+      "package/**/*.js", // Generated/compiled JavaScript from TypeScript
+      "package/**/*.d.ts" // Generated TypeScript declaration files
     ]
   },
 
@@ -63,7 +64,11 @@ module.exports = [
       "import/no-extraneous-dependencies": "off",
       // TypeScript handles extensions, not needed for JS imports
       "import/extensions": "off",
-      indent: ["error", 2]
+      indent: ["error", 2],
+      // Allow for...of loops - modern JS syntax
+      "no-restricted-syntax": "off",
+      // Allow console statements - used for debugging/logging throughout
+      "no-console": "off"
     },
     settings: {
       react: {
@@ -130,13 +135,120 @@ module.exports = [
       "@typescript-eslint/no-use-before-define": ["error"],
       "@typescript-eslint/no-unused-vars": [
         "error",
-        { argsIgnorePattern: "^_" }
+        { argsIgnorePattern: "^_", varsIgnorePattern: "^_" }
       ],
       "@typescript-eslint/no-explicit-any": "error",
-      "@typescript-eslint/explicit-module-boundary-types": "off"
+      "@typescript-eslint/explicit-module-boundary-types": "off",
+      "no-undef": "off"
     }
   },
 
+  // Global rule for all TypeScript files in package/
+  // Suppress require() imports - these are intentional for CommonJS compatibility
+  // Will be addressed in Phase 3 (breaking changes) - see #708
+  {
+    files: ["package/**/*.ts"],
+    rules: {
+      "@typescript-eslint/no-require-imports": "off",
+      "global-require": "off",
+      "import/no-import-module-exports": "off"
+    }
+  },
+
+  // Consolidated override for package/config.ts and package/babel/preset.ts
+  {
+    files: ["package/babel/preset.ts", "package/config.ts"],
+    rules: {
+      "@typescript-eslint/no-unused-vars": "off",
+      "import/order": "off",
+      "import/newline-after-import": "off",
+      "import/first": "off",
+      "@typescript-eslint/no-explicit-any": "off",
+      "no-useless-escape": "off"
+    }
+  },
+
+  // configExporter module overrides
+  {
+    files: ["package/configExporter/**/*.ts"],
+    rules: {
+      "@typescript-eslint/no-use-before-define": "off",
+      "import/no-dynamic-require": "off",
+      "class-methods-use-this": "off",
+      "import/prefer-default-export": "off",
+      "no-underscore-dangle": "off",
+      "no-restricted-globals": "off",
+      "@typescript-eslint/no-unused-vars": "off",
+      "@typescript-eslint/no-explicit-any": "off"
+    }
+  },
+
+  // Utils module overrides
+  {
+    files: [
+      "package/utils/inliningCss.ts",
+      "package/utils/errorCodes.ts",
+      "package/utils/errorHelpers.ts",
+      "package/utils/pathValidation.ts",
+      "package/utils/getStyleRule.ts",
+      "package/utils/helpers.ts",
+      "package/utils/validateDependencies.ts",
+      "package/webpackDevServerConfig.ts"
+    ],
+    rules: {
+      "@typescript-eslint/no-explicit-any": "off",
+      "no-useless-escape": "off"
+    }
+  },
+
+  // Plugins and optimization overrides
+  {
+    files: ["package/plugins/**/*.ts", "package/optimization/**/*.ts"],
+    rules: {
+      "import/prefer-default-export": "off"
+    }
+  },
+
+  // Rules, rspack, swc, esbuild, and other modules
+  {
+    files: [
+      "package/index.ts",
+      "package/rspack/index.ts",
+      "package/rules/**/*.ts",
+      "package/swc/index.ts",
+      "package/esbuild/index.ts",
+      "package/dev_server.ts",
+      "package/env.ts"
+    ],
+    rules: {
+      "@typescript-eslint/no-unused-vars": "off",
+      "import/prefer-default-export": "off",
+      "no-underscore-dangle": "off"
+    }
+  },
+
+  // Environments module overrides
+  {
+    files: ["package/environments/**/*.ts"],
+    rules: {
+      "import/prefer-default-export": "off",
+      "no-underscore-dangle": "off"
+    }
+  },
+
+  // Type tests are intentionally unused - they test type compatibility
+  {
+    files: ["package/**/__type-tests__/**/*.ts"],
+    rules: {
+      "@typescript-eslint/no-unused-vars": "off"
+    }
+  },
+
+  // Note: Type-aware rule overrides from main config (e.g., @typescript-eslint/no-unsafe-*,
+  // @typescript-eslint/restrict-template-expressions) are intentionally omitted here since
+  // fast mode doesn't enable type-aware linting (no parserOptions.project specified).
+  // This keeps fast mode performant while maintaining consistency for non-type-aware rules.
+
   // Prettier config must be last to override other configs
   prettierConfig
 ]