Add a '⬡ forge ↗' link to the per-agent page's meta row, next to
the stats + screen links. It opens the agent's Forgejo profile
(http://<host>:3000/<label> — the per-agent forge user is named
after the agent) in a new tab.
- web_ui.rs: StateSnapshot gains forge_present, true when the
agent's forge-token file exists in the state dir (same signal
that tells the agent it has a forge account).
- index.html / app.js: hidden link, shown + href-filled when
forge_present, mirroring the existing gui_enabled/screen-link
pattern. Host comes from window.location so it works off
whatever host the page is served from.
closes#185
6ab667901d