Confirm Call Publisher

Re-check ownership AFTER the asking tab has joined the room.

Publish permission is baked into a token when it is minted, and revoking it is a one-shot action against a participant who has to already be in the room — UpdateParticipant on someone absent is a 404, which we deliberately read as "not publishing, nothing to do".

Those two facts leave a window. A tab mints a publish-capable token, and before it finishes connecting the operator answers in another tab: the claim displaces it in the registry and revokes a participant who does not exist yet. A moment later it joins with the token it already holds, publishes, and nothing ever contradicts it — LiveKit fires no permission change because nothing changed after it joined. The registry says one owner and the room has two: the operator hears themselves, and the tab that lost draws full call chrome for a call it does not own (reported repeatedly 2026-08-03; the bridge logged both browser identities subscribing to one call).

So the joined tab asks once, at the only moment its presence is certain, and a tab that is not the holder is revoked here — which is what the overlays' participantPermissionsChanged handler already reacts to. The answer is the registry's, so it holds across browser profiles and devices, unlike the BroadcastChannel election.