[Test] Exclude .claude/worktrees from vitest

Stale agent worktrees under .claude/ contain old code copies that vitest's
default exclude doesn't ignore, producing false test failures during the
project test run. Adds **/.claude/** to the exclude list while preserving
the standard defaults.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

vitest.config.ts

@@ -5,6 +5,12 @@ export default defineConfig({
   test: {
     environment: "jsdom",
     globals: true,
+    exclude: [
+      "**/node_modules/**",
+      "**/dist/**",
+      "**/.{idea,git,cache,output,temp}/**",
+      "**/.claude/**",
+    ],
   },
   resolve: {
     alias: {