- Terminals were never destroyed when their tab closed (socket drop only
detached listeners), so the per-session quota (3) filled up and new
terminals failed to mount with 'terminal limit reached'. Now the client
sends a {type:'close'} control frame on tab teardown and the host releases
the pty immediately; a bare socket drop (refresh/switch) keeps the process
for a 30s grace period, and a reconnect within it cancels the pending
close. open() also respawns a process whose shell already exited instead
of reusing a dead handle (input sink).
- The sidebar portal renders inside an error boundary: a render failure now
shows a dismissible error strip with the message (console.error with the
component stack) instead of a silent blank panel.
- Tests: +2 real-pty smoke specs (close releases quota + respawn after
exit; reconnect cancels pending close).