refactor: migrate to Vercel-native deployment for branch status pages

- Remove GitHub Pages workflow (release-pages.yml)
- Add Vercel configuration (vercel.json)
- Create artifact fetcher script (scripts/fetch-branch-artifacts.sh)
  - Fetches Storybook from Cloudflare Pages
  - Downloads E2E/Vitest reports from GitHub Actions
  - Uses gh CLI for API access
- Update build script with graceful fallbacks
  - Creates placeholder pages for pending CI
  - Supports both local and Vercel environments
  - Handles missing artifacts gracefully
- Add pages:build:branch-status npm script
- Update documentation with new deployment approach

Benefits:
- Deploys immediately on every push
- Fetches artifacts on-demand during build
- Shows loading states for pending CI
- Simpler, more reliable architecture
- No complex artifact passing between GitHub Actions and Vercel

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

package.json

@@ -12,6 +12,7 @@
     "build-storybook": "storybook build",
     "build:types": "nx build --config vite.types.config.mts && node scripts/prepare-types.js",
     "build:analyze": "cross-env ANALYZE_BUNDLE=true pnpm build",
+    "build:branch-status": "...",
     "build": "cross-env NODE_OPTIONS='--max-old-space-size=8192' pnpm typecheck && nx build",
     "size:collect": "node scripts/size-collect.js",
     "size:report": "node scripts/size-report.js",
@@ -37,6 +38,7 @@
     "locale": "lobe-i18n locale",
     "oxlint": "oxlint src --type-aware",
     "pages:build": "bash scripts/build-pages.sh && vite build --config ./.pages/vite.config.ts",
+    "pages:build:branch-status": "bash scripts/fetch-branch-artifacts.sh && bash scripts/build-pages.sh && vite build --config ./.pages/vite.config.ts",
     "pages:dev": "vite --config ./.pages/vite.config.ts",
     "preinstall": "pnpm dlx only-allow pnpm",
     "prepare": "husky || true && git config blame.ignoreRevsFile .git-blame-ignore-revs || true",