cdidx index can self-interrupt during full rebuild and leave the local index empty

[Widthdom]

Summary

While working on #1779, repeated local index refresh attempts on fix-issue1779 ended with E012_INTERRUPTED even though no Ctrl-C was sent manually. A subsequent status showed the index had 0 files and degraded readiness.

Commands observed

• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll index . --rebuild --yes --json
  • failed at 471/483 with Interrupted; partial progress saved... E012_INTERRUPTED
• CDIDX_INDEX_PARALLELISM=1 dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll index . --rebuild --yes --json
  • failed at 332/483 with the same E012
• CDIDX_INDEX_PARALLELISM=1 dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll index . --json
  • failed at 235/483 with the same E012
• status --check --json after interruption showed files: 0, index_matches_workspace: false, and degraded graph_table_available, issues_table_available, and fold_ready readiness.

Expected

A rebuild should either complete or fail with a cause that does not leave the main local index in an empty/degraded state without a reliable recovery path.

Environment

macOS arm64, local repository workspace, branch fix-issue1779 at ca167e7527815901c8e189f29390896ffcdf256c.

[Widthdom]

Work started on branch codex/fix-issue2642.