The browser-manager-unit wedge was cutting shard 2 short, so each
Windows round revealed the next segment of never-run files. With the
wedge excluded, shard 2 completes (50s) and shows its real failures:
seven more POSIX-environment files (PID/cmdline identity probing,
bash scripts as the subject under test, env-scrubbed bun spawns).
Shards 1 and 3 (including all tree-mutators) now PASS on
windows-latest — this should be the fixed point: ~234 files of real
Windows coverage vs the 13 hand-picked before.