Live portal: Go Live — browser window capture published over WHIP as <user>/HelmetCam-<date>; dumpd /me/stream-key

Go Live closes viewer windows, fetches the Authentik-identified user's MediaMTX key from dumpd
(/etc/vanguard/streamers.json written by configure.py), opens Chrome's window-only picker with
audio, prefers H.264 so MediaMTX can record, caps at 12 Mbps / 1440p60, shows live stats, Stop.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

README.md

@@ -199,6 +199,10 @@ asked by `configure.py --full`) can post when a stream starts.
    embedded outpost → group policy (e.g. everyone in the server, or `streamers`+`editors`+`admins`).
 3. Dev box: `./deployLive.sh` builds `live/` and copies `dist/` to `/srv/live` (Caddy serves it directly).
 
+**Go Live** button: broadcast a window from the browser (no OBS) as `<user>/HelmetCam-<date>` — key comes
+from `/me/stream-key` (dumpd reads `/etc/vanguard/streamers.json`, identity from the Authentik header), so a
+streamer's Authentik username must equal their MediaMTX name.
+
 Bandwidth: no transcoding, every viewer gets the source bitrate (~15 Mbps) → ~30 concurrent viewers on
 the 500 Mbps line. For a crowd, restream to Twitch from OBS.