feat(site): auto-sync + auto-suggest adapters (auto-trigger)

Make `site` trigger itself so an agent doesn't have to know adapters exist.

Auto-sync: the pack refreshes on first use and on a TTL (default 7d), both in
the `site` command path (blocking, fast) and as a non-blocking background task
on daemon startup — so ~/.chrome-use/sites/.index.json is always populated with
zero added latency. Tune via AGENT_BROWSER_SITES_TTL_DAYS; disable with
AGENT_BROWSER_SITES_NO_AUTO_UPDATE=1. `update` now writes .last_update + a
domain→adapters .index.json (read-only adapters ordered first).

Auto-suggest: `open`/`navigate`/`snapshot` onto a domain with adapters attaches
`siteAdapters: {domain, commands}` to the response; the CLI prints a
`💡 site adapters for <domain>` hint (stderr) and the field rides along in --json.
SKILL.md tells the agent to prefer the listed `site <name>/<cmd>` over scraping.
This keeps the 'never auto-disrupt user tabs' guarantee — it suggests, the agent
decides; nothing auto-runs on navigation.

site.rs: needs_refresh/adapters_for_domain/write_domain_index + timestamp/index
in update(). daemon.rs: background bootstrap. actions.rs: with_site_hint on
navigate + snapshot. output.rs: hint render. Verified live: open github.com →
hint leads with read-only github/issues; --json carries siteAdapters.

README.zh.md

@@ -188,6 +188,20 @@ chrome-use site bilibili/feed --json            # 能用，因为走的是你的
 位置参数按适配器声明的参数顺序填入；`--key value` 按名覆盖。适配器由 bb-sites 社区编写、
 版权归各自作者所有 —— chrome-use 只负责运行它们。
 
+**自动同步 + 自动提示。** 你基本不用手动 `site update`:chrome-use 首次使用时自动拉取,
+之后每周后台刷新一次(`AGENT_BROWSER_SITES_TTL_DAYS` 调周期,`AGENT_BROWSER_SITES_NO_AUTO_UPDATE=1`
+关闭)。而当你 `open`/`snapshot` 一个有适配器的域名时,chrome-use 会在输出里直接把可用命令
+亮出来 —— 一行 `💡 site adapters for <域名>`,`--json` 下则是 `siteAdapters` 字段 —— 这样
+agent 会直接改用结构化适配器,而不是去扒 DOM:
+
+```text
+$ chrome-use open https://github.com
+💡 site adapters for github.com — prefer these for structured data:
+   github/issues, github/me, github/repo, …
+   e.g. chrome-use site github/issues --json
+✓ GitHub
+```
+
 ## 自动化测试（`chrome-use test`）
 
 把反复的「打开它、点一圈、看对不对」变成**可重跑的测试套件** —— 前端的单元测试。用 YAML 写用例；步骤复用 chrome-use 自己的命令，断言编译成一次检查：