fix: build script vite --root incompatibility

Replace `npx vite build --root web` with `npm run build:web`
which uses the existing `cd web && npx vite build` approach.

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

package.json

@@ -9,7 +9,7 @@
     "dev": "tsx watch src/index.ts",
     "dev:web": "cd web && npx vite",
     "build:web": "cd web && npx vite build",
-    "build": "npx vite build --root web && tsc",
+    "build": "npm run build:web && tsc",
     "start": "node dist/index.js",
     "check-update": "tsx scripts/check-update.ts",
     "check-update:watch": "tsx scripts/check-update.ts --watch",