Feat/douban book subject

[warkcod]

Description

Extend the existing Douban adapter to support book subject details and make douban search --type book reliable enough for metadata enrichment workflows.

This PR includes:

• support for opencli douban subject <id> --type book
• normalized book metadata fields from book.douban.com
• fixes for opencli douban search --type book
• adapter tests, browser e2e coverage, and Douban docs updates

Related issue:

• N/A

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🌐 New site adapter
• 📝 Documentation
• ␌ Refactor
• 🔧 CI / build / tooling

Checklist

• I ran the checks relevant to this PR
• I updated tests or docs if needed
• I included output or screenshots when useful

Documentation (if adding/modifying an adapter)

• Added doc page under docs/adapters/ (if new adapter)
• Updated docs/adapters/index.md table (if new adapter)
• Updated sidebar in docs/.vitepress/config.mts (if new adapter)
• Updated README.md / README.zh-CN.md when command discoverability changed
• Used positional args for the command's primary subject unless a named flag is clearly better
• Normalized expected adapter failures to CliError subclasses instead of raw Error

Screenshots / Output

Example commands

opencli douban search --type book "三体" -f json
opencli douban subject 2567698 --type book -f json

### Verification

npm run test
OPENCLI_E2E=1 npx vitest run --project e2e tests/e2e/douban.test.ts
npm run build

### Result summary

- npm run test: passed
- OPENCLI_E2E=1 npx vitest run --project e2e tests/e2e/douban.test.ts: passed
- npm run build: passed