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.

skill-data/core/SKILL.md

@@ -218,6 +218,13 @@ chrome-use site github/issues owner/repo --json   # run it → JSON (navigates t
 - If no adapter fits, fall back to the normal `snapshot`/`eval` loop. Adapters come from the
   [bb-sites](https://github.com/epiral/bb-sites) community pack; chrome-use fetches & runs them.
 
+> **Auto-trigger — act on it.** chrome-use keeps the pack synced automatically (first use +
+> weekly), and when you `open`/`navigate`/`snapshot` a page whose domain has adapters it tells
+> you: a `💡 site adapters for <domain>` line on stderr, and a `siteAdapters: {domain, commands}`
+> field in `--json`. **When you see that, prefer the listed `site <name>/<cmd>` over snapshot+click
+> for reading data** — it's the cheaper, more reliable path and it's already installed. You don't
+> need to run `site update` yourself; just use the command it names.
+
 ## Quickstart
 
 ```bash