fix: exclude test files from webpack TypeScript checking

Exclude src/**/*.test.* and src/**/*.spec.* from tsconfig.json so the
webpack dev server's ForkTsCheckerWebpackPlugin doesn't type-check them
(they use jest globals not available in the webpack context).

Add tsconfig.lint.json (extends tsconfig.json, re-includes test files)
and point eslint at it so type-aware linting still covers tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: arbrandes

eslint.config.js

@@ -19,4 +19,15 @@ module.exports = createLintConfig(
       '**/__snapshots__/*',
     ],
   },
+  {
+    // Test files are excluded from tsconfig.json to prevent the webpack dev server's
+    // ForkTsCheckerWebpackPlugin from type-checking them. Use a separate tsconfig for
+    // eslint that re-includes test files for type-aware linting.
+    languageOptions: {
+      parserOptions: {
+        projectService: false,
+        project: './tsconfig.lint.json',
+      },
+    },
+  },
 );

tsconfig.json

@@ -15,5 +15,9 @@
     "eslint.config.js",
     "jest.config.js",
     "site.config.*.tsx"
+  ],
+  "exclude": [
+    "src/**/*.test.*",
+    "src/**/*.spec.*"
   ]
 }

tsconfig.lint.json

@@ -0,0 +1,12 @@
+{
+  "extends": "./tsconfig.json",
+  "include": [
+    "src/**/*",
+    "app.d.ts",
+    "babel.config.js",
+    "eslint.config.js",
+    "jest.config.js",
+    "site.config.*.tsx"
+  ],
+  "exclude": []
+}