Support Brave Talk (iframe-embedded JaaS/8x8.vc Jitsi deployments)

[thiphu1012]

Summary

Adds Brave Talk support (and any other JaaS/8x8.vc-backed white-labeled Jitsi embed) by making
the Jitsi join, admission, and capture/recording code frame-aware.

Closes #1512.

Context

JaaS/8x8.vc-backed deployments — Brave Talk (talk.brave.com) among them — render the entire
conference app (prejoin, lobby, conference, media elements) inside a cross-origin <iframe>. The
top-level page has no jitsi DOM of its own. Stock meet.jit.si and most self-hosted deployments
render at the top level instead, and are unaffected either way.

Every DOM/API check in join.ts, admission.ts, and capture-bridge.ts used
page.evaluate() / page.locator(), which only reach the top frame — so on Brave Talk the bot:

1. Never found the prejoin name field or Join button (logged a false
   "No prejoin name field detected" and looped on "waiting for admission" forever, having
   never actually entered the room).
2. Once join itself was patched, isAdmitted()/getAppJoinedState() still couldn't see
   window.APP or the hangup button (both live in the iframe), so admission looked "unknown."
3. Once admission was patched too, startCaptureBridge/startRecording still targeted the top
   frame, so record-chunker found zero <audio>/<video> elements and produced no transcript
   despite the bot visibly sitting in the call.

Fix

• New: core/meetings/modules/join/src/jitsi/frame-utils.ts — a shared frame-scanning
  utility (allJitsiFrames, findFrameWithVisibleSelector, isVisibleInAnyFrame, scanFrames,
  resolveConferenceFrame). Every helper tries the top frame first — byte-identical behavior for
  the un-iframed case — then falls back to scanning child frames. Exported from @vexa/join's
  public index for reuse by the bot service.
• jitsi/join.ts: the prejoin name-field / Join-button lookup now uses
  findFrameWithVisibleSelector and scopes the fill + click to whichever frame it actually found
  the field in.
• jitsi/admission.ts: getAppJoinedState, getLobbyState, isHangupVisible, the prejoin/
  conference/lobby DOM checks, and the rejection/removal text scan all now scan every frame
  instead of just the top one.
• capture-bridge.ts: startCaptureBridge, startRecording, and the speak path's mic
  toggle resolve the actual conference frame (resolveConferenceFrame — the frame that has
  <audio>/<video> elements) and target it for setup, teardown, and control, only when
  platform === 'jitsi' — every other platform (and stock/self-hosted Jitsi) is untouched.

page.exposeFunction() and context.addInitScript() already install into every frame by
Playwright's own design (confirmed in this file's existing comments), so the PCM audio bridge and
window.VexaBrowserUtils needed no changes — only the invocation side needed frame-targeting.

Docs

• docs/docs/how-to/send-a-bot.mdx — Jitsi tab now shows a Brave Talk example and notes that
  bare-URL auto-detection doesn't yet cover non-8x8.vc hosts (tracked as a follow-up in Jitsi bot can't join or transcribe iframe-embedded deployments (Brave Talk / JaaS/8x8.vc) #1512).
• docs/changelog.d/1513-jitsi-iframe-frame-awareness.md — per-PR changelog fragment (docs-current
  / ADR-0032).

Test case

Live end-to-end verification against a real Brave Talk room (talk.brave.com), self-hosted
compose stack, make bot build of this branch:

1. Before fix: bot navigates to the room, logs "No prejoin name field detected — proceeding to admission checks", loops "Still waiting for admission" until the escalation VNC debug
   view confirms the browser is still sitting on the pre-join screen with the name field visibly
   pre-filled ("PT's notetaker") — the bot just never saw it.
2. After join+admission fix: bot logs "Name entered" → "Join clicked" →
   "Bot immediately admitted (no lobby)". Confirmed via the meeting API (status: "active").
3. After capture fix: page console logs "[record-chunker] 1 media elements (strict)" →
   "connected element 1/1" → "combined 1 streams" → "MediaRecorder started". Polling
   GET /transcripts/jitsi/{room} returns real transcribed segments matching what was spoken
   into the call, e.g.:

   { "text": "Hello, this meeting will have a discussion about the chop head...",
     "language": "en", "completed": true }

4. Regression check: existing unit tests (admission.test.ts, join.test.ts) pass unchanged —
   the test page stub was extended with frames()/mainFrame() returning itself, so
   allJitsiFrames() degenerates to exactly the prior single-frame behavior for these tests.
   npx tsx src/jitsi/admission.test.ts → 6/6 pass; npx tsx src/jitsi/join.test.ts → 11/11
   pass.
5. Full make bot image build (TypeScript compile across the whole @vexa/bot build scope)
   succeeds clean.

Deployment validated: self-hosted Compose (make all + make bot), macOS host via OrbStack,
fresh clone of main at 6d6d38a2, self-hosted CPU transcription unit (small → medium
model). Not yet validated on Lite or k8s/Helm.

Known follow-up (not in scope here)

• password.ts's room-password dialog handling is still top-frame-only — an iframe-embedded,
  password-protected Jitsi room would need the same treatment. Not hit by Brave Talk (no password
  prompt in this flow).
• Bare-meeting_url platform auto-detection (resolvePlatform) doesn't recognize
  talk.brave.com or other non-8x8.vc JaaS custom domains — platform must be sent explicitly
  for now (documented above).

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🃏 Merge card — #1513

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