gate-miss: PR #309 cross-platform Git probe cleanup coverage #312

PR: #309
Found at: pre-merge
Signal: unverified-item
Defect: The gate lacks real Windows coverage for Git timeout cleanup and non-macOS scheduling command rejection, and does not establish bounded cleanup under uninterruptible kernel I/O.
Expected check: none
Class: automatable
Conversion: Add a Windows fake-Git process fixture and CLI smoke check when Windows CI is introduced; retain uninterruptible-I/O cleanup as an explicit manual limitation, revisiting it on the first observed stalled cleanup.

This is a coverage gap, not a reproduced Windows defect. macOS process-group cleanup, error propagation, identity retention, lock release, large output, and subsequent manual lock acquisition were tested. Non-macOS unit checks exercise platform rejection on Linux, but real Linux/Windows CLI installations were not exercised locally. Windows stops and waits for the direct child; descendant behavior is unverified. The post-kill wait has no independent deadline, so a hard-mounted NFS stall can still retain the lock. CI does not prove that case.