[umpireboulianne-design]

Fixes #1327

Summary

• Decode subprocess output with replacement (check_one): Pass encoding="utf-8", errors="replace" to subprocess.run in check_one so non-UTF-8 bytes in compiler diagnostics do not raise UnicodeDecodeError and abort the fuzz campaign.
• Resilient corpus loading (load_corpus): Filter os.listdir(corpus_dir) with os.path.isfile(...) so .hy directories do not raise IsADirectoryError, and read corpus seed files with encoding="utf-8", errors="replace" so byte-mutated seeds do not crash startup.
• Fail closed on non-executable --hyb (main): Validate os.access(args.hyb, os.X_OK) during CLI startup and exit immediately with code 2 and a diagnostic on stderr instead of running 10 doomed cases.
• Accurate executed case count on early stop (main): Track actual executed cases in the fuzz loop and print {executed} cases in the summary line rather than the requested args.cases when aborting early after 10 failures.

Testing

• Added regression tests in tools/fuzz/test_hyfuzz.py covering non-UTF-8 subprocess output (normal reject and ICE detection), .hy directories and non-UTF-8 corpus seeds in load_corpus, non-executable --hyb startup rejection, and accurate case count reporting on early abort.

[limitlessprojects]

Queue-reset sweep: this repo now runs a rolling conveyor, and open PRs
outside the active review window are being closed as not planned to keep the
queue honest — a stale queue wastes every contributor's time, including yours.

This is not a verdict on the work. If this change still matters:

1. rebase against current main (main has landed a lot since this PR opened),
2. confirm the diff still applies and the affected verdicts still hold,
3. reopen — the triage board picks reopened PRs up as fresh arrivals.

Wildcard holds (verdict window 2026-11-01) and Pareto land candidates are
unaffected. Thanks for the effort — high-volume repos only stay reviewable
with a queue that actually drains.