feat: add agent-mail skill, parsed mail API and docs (#993)

* feat: add cf-temp-mail-usage skill and parsed mail API for AI agents

- feat: new /api/parsed_mails and /api/parsed_mail/:id endpoints returning
  server-parsed subject/text/html/attachments metadata (reuses commonParseMail)
- feat: add .claude/skills/cf-temp-mail-usage read-only skill so AI agents
  (OpenClaw / Codex / Cursor) can consume a mailbox with a user-supplied JWT,
  bypassing the Turnstile challenge required for mailbox creation
- refactor: split mails_api/index.ts and admin_api/index.ts into thin route
  shells; move business logic into dedicated *_api.ts files
- docs: update README / README_EN / CHANGELOG with agent-email feature and
  npx degit install instructions for the skill

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* feat: rename skill to cf-temp-mail-agent-mail, add agent-email docs, fix sender trim

- Rename skill from cf-temp-mail-usage to cf-temp-mail-agent-mail
- Rewrite SKILL.md: parsed API primary, local fallback, prerequisites, multi-agent install
- Add vitepress docs (zh + en) for AI Agent mailbox usage
- Fix leading space in parsed_mail_api sender field via .trim()
- Update README install section with 3 install methods
- Update changelogs (zh + en)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* docs: simplify README agent skill section to one-liner with links

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* feat: add send mail API to skill, credential persistence, remove poll example

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -150,6 +150,7 @@
 - [x] Webhook 支持，消息推送集成
 - [x] 支持 `CF Turnstile` 人机验证
 - [x] 限流配置，防止滥用
+- [x] **Agent 友好**：内置 [`cf-temp-mail-agent-mail`](.claude/skills/cf-temp-mail-agent-mail/SKILL.md) skill，AI agent 可直接消费邮箱，详见 [文档](vitepress-docs/docs/zh/guide/feature/agent-email.md)
 
 </details>