fix(msteams): dismiss 'Continue without audio or video' modal before Join (closes #226)

[muhzak]

Summary

• Closes [Bug] Teams bot stuck on light-meetings/launch: 'Continue without audio or video?' modal blocks Join #226. Reproduced verbatim in a fresh self-hosted compose deploy of v0.10.3 against teams.microsoft.com/meet/<numeric>?p=<passcode> URLs.
• Bot was timing out at awaiting_admission for 15 min on every attempt because the underlying Join now button stays in the DOM (so waitForTeamsPreJoinReadiness returns "ready") but the actual click is intercepted by the post-decline confirmation modal in the nested light-meetings/launch iframe.
• Patch dismisses the modal in the joiner's modal-handling step before Step 6: Clicking 'Join now'. Probe is gated on isVisible({ timeout: 500 }) and falls through silently when no modal is present, so flows that don't hit this overlay are unaffected.
• Iterates page.frames() because the modal renders inside light-meetings/launch, not the top frame — first patch attempt missed it for that reason.

Repro before the patch

[BotCore] Step 6: Clicking 'Join now' to enter the meeting...
[BotCore] ⚠️ Join button not found — bot may not be able to enter the meeting
[BotCore] Found Teams waiting room indicator: lobby text or Join now button visible - Bot is still in waiting room
[BotCore] Bot is in Teams waiting room. Waiting for 900000ms for admission...
[BotCore] Still in Teams waiting room... 2s elapsed
... (loops to 15-min timeout)

After

[BotCore] Step 6: Clicking 'Join now' to enter the meeting...
[BotCore] ✅ Clicked 'Join now' button
[BotCore] 🔥 UNIFIED CALLBACK: AWAITING_ADMISSION - reason: none

Bot reaches the host's lobby and is admittable. Verified end-to-end: bot joined → admitted by host → meeting completed → audio recorded to MinIO → readable from /recordings/{id}/media/{media_id}/raw.

Notes

• Selector covers both the long-form "Continue without audio or video" button and the short "Continue" fallback, in case Teams shortens the label in a UI rev.
• The probe runs once per join attempt right before the existing Step 6, so it composes cleanly with the upstream Teams reliability epic in epic: Teams reliability — admission, avatar, chat, and join-modal handling #252 — this fix can land without blocking the larger reliability cycle.