Exclude tests/bench from vitest test discovery

The bench fixtures are plain Ember source files, not test files.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: NullVoxPopuli

vitest.config.mjs

@@ -5,7 +5,7 @@ export default defineConfig({
     globals: true,
     setupFiles: [],
     include: ['**/tests/**/*.js'],
-    exclude: ['tests/helpers/**', 'node_modules'],
+    exclude: ['tests/helpers/**', 'tests/bench/**', 'node_modules'],
     sequence: {
       hooks: 'list',
     },