fix: quarantine files on EXIT_NONZERO instead of aborting chunk

[shashwatMishra96]

When a worker process exits with a nonzero code (e.g. internal parse-limit abort on a pathological file), treat it the same as CRASH/HANG: quarantine the offending file via the existing two-consecutive-strikes mechanism and continue indexing the rest of the chunk.

Previously, EXIT_NONZERO caused the supervisor to abort the entire chunk, losing all indexed data for that directory. This is impactful for large-scale repos (Android AOSP: 253GB, 60M+ files) where machine-generated files routinely trigger internal limits.

The two-consecutive-strikes intersection mechanism already guards against false quarantines — a systemic nonzero exit (e.g. bad CLI arg) produces no recurring suspect, so the intersection is empty and the supervisor gives up (same behavior as before).

Tested on Android QSSI17 (253GB, 24 chunks) + QCM6490 vendor (244 chunks). Result: 11.35M nodes indexed, 0 data loss, 2 genuinely pathological files quarantined (checkpatch.pl, a 140K-line generated .ts file).

What does this PR do?

Checklist

• Every commit is signed off (git commit -s) — required, CI rejects
  unsigned commits (DCO, see CONTRIBUTING.md)
• Tests pass locally (make -f Makefile.cbm test)
• Lint passes (make -f Makefile.cbm lint-ci)
• New behavior is covered by a test (reproduce-first for bug fixes)

[github-actions]

Thanks for opening this — it has been seen, and it is queued.

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Current review status: working through a backlog. 0.9.1-rc.1 is out, so the release freeze that held reviews is over — but it left a large queue of open pull requests behind it, and we are reading through them oldest-first. The background is in discussion #1144.

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