16 tests for the file-based handshake: round-trip, clear, permissions,
atomic write tmp-file cleanup, excerpt sanitization (truncation, ctrl
chars, whitespace collapse), and a simulated poll-loop confirming
allow/block/timeout behavior the sidebar-agent relies on.
Pins the contract so future refactors can't silently break the
allow-path recovery and ship people back into the hard-kill FP pit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
