cdidx import should bound archive entry size before extraction

[Widthdom]

Summary

cdidx import extracts codeindex.db from a zip archive without checking compressed or uncompressed size. A crafted archive can force excessive disk writes before SQLite validation runs.

Evidence

• src/CodeIndex/Cli/ExportImportCommandRunner.cs:79 obtains the codeindex.db entry.
• src/CodeIndex/Cli/ExportImportCommandRunner.cs:83 calls dbEntry.ExtractToFile(tempPath, overwrite: true) with no entry length or copy limit check.
• Validation with DbContext.TryValidateExistingCodeIndexDb happens only after the extraction completes.

Expected

Import should enforce a maximum uncompressed database size and fail before or during extraction when the archive exceeds that bound.

[Widthdom]

Work started on branch fix-issue2834-2835.