Previously: peer hangs up → Rust emits signal-event {type:hangup}
→ JS clears callStatusText + hides incoming panel, but the call
screen stays on with a dangling Hangup button the user has to
press to acknowledge a call that's already over. Dead UX.
Now: the hangup event handler tears down our side of the media
engine via `invoke("disconnect")` and transitions back to the
connect screen when we're currently in the call screen.
Incoming-call panel still hides as before.
`userDisconnected = true` is set so the existing call-event
"disconnected" auto-reconnect path (which fires on transport
drop) doesn't kick in — the peer-hangup signal is an intentional
end-of-call, not a transport blip worth retrying.
Also documented: "not connected" errors from the `disconnect`
command are silently swallowed because they happen when there's
no engine to tear down (e.g. incoming call that was never
answered — caller bailed), which is the correct outcome there.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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