The review's three remaining items:
- A regression test rebinds __main__.ProtocolChannel.read_frame_async and asserts
a binding reply still round-trips (the pump's reader is a bound method
captured by _run before the program runs).
- The settlement note (en + zh) records that send_done's frame-shape check uses
_run's bound _str/_isinstance.
- The staging-removal comment no longer claims teardown retries tracked state:
teardown deliberately does not sweep staging, so a removal failure is the one
case the gone-by-settlement contract degrades on.
Pairing re-recorded.