feat(site): bb-sites adapters — turn any site into a structured-data CLI

Add `chrome-use site` — run community bb-sites adapters over chrome-use's
stealth transport. An adapter is a per-command JS function that calls a
site's own JSON API from inside your logged-in tab (your cookies, same-origin
fetch, the site's modules) and returns clean JSON — no clicking/scraping.

- site update   fetch the upstream bb-sites pack into ~/.chrome-use/sites
- site list     list installed adapters (name/cmd)
- site info     show an adapter's @meta (args, domain, capabilities)
- site <name>/<cmd> [args]  navigate to its domain (reuse tab if already there) + eval, return JSON

chrome-use ships zero adapter code; `site update` fetches epiral/bb-sites at
runtime (like a package manager). Adapters remain their authors' property.

cli/src/site.rs (load/parse/build_eval/list/update/map_args + tests), wired
via commands.rs (parse), actions.rs (handle_site), main.rs (CLI dispatch).
Docs in README, README.zh, skill-data/core. Verified live: github/issues
returned 30 real issues as JSON over the relay.

cli/Cargo.lock

@@ -290,7 +290,7 @@ checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
 
 [[package]]
 name = "chrome-use"
-version = "1.5.18"
+version = "1.5.19"
 dependencies = [
  "aes",
  "aes-gcm",