* fix(dashboard): close PTY WebSocket on child EOF to stop FD leak
The /api/pty handler's reader task returns on child EOF, but the writer
loop stayed blocked on ws.receive() until the browser sent a disconnect.
When the browser socket is half-open (no FIN delivered — common on
macOS/launchd), that disconnect never arrives, so the handler never
reaches its finally and the PTY master fd + child process leak. With
dashboard auto-reconnect (#52962), every dropped socket then spawns a
fresh PTY on top of the orphaned one, exhausting file descriptors within
hours (EMFILE / Errno 24).
Fix: the reader task now closes the WebSocket in a finally when the child
EOFs or the send side breaks, which unblocks ws.receive() so the existing
finally runs bridge.close(). The writer loop also guards ws.receive()
against the RuntimeError Starlette raises once the socket is closed.
Reported by @fifteenzhang.
Fixes#54028
* docs: add infographic for #54028 PTY FD leak fix
6d879d486b