fix(server): warn and skip non-numeric filenames in consumer offset directories instead of panicking

[atharvalade]

Which issue does this PR close?

Closes #3132

Rationale

An operator accidentally placing a file (e.g. .DS_Store, editor swap file, backup) in the consumer offsets directory crashes the server on startup due to a panic! on non-numeric filenames.

What changed?

Both load_consumer_offsets and load_consumer_group_offsets in core/server/src/streaming/partitions/storage.rs panicked when encountering files with non-numeric names during startup offset loading.

The fix replaces both panic! calls with warn! log messages and continue, so the server gracefully skips unexpected files. Added 9 integration tests in core/integration/tests/storage/consumer_offsets.rs covering valid files, non-numeric files (.DS_Store, backup.bak), empty directories, subdirectories, and nonexistent paths for both functions.

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

1. Opus 4.6
2. Minimal AI used
3. All tests verified locally with cargo test, cargo clippy, cargo fmt --check, and CI scripts
4. Yes, all code can be explained

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.69%. Comparing base (611fca0) to head (5ef2977).

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3135       +/-   ##
=============================================
- Coverage     74.10%   52.69%   -21.41%     
  Complexity      943      943               
=============================================
  Files          1159     1157        -2     
  Lines        102033    90321    -11712     
  Branches      79083    67389    -11694     
=============================================
- Hits          75607    47596    -28011     
- Misses        23765    40157    +16392     
+ Partials       2661     2568       -93     

Components	Coverage Δ
Rust Core	46.47% <100.00%> (-28.86%)	⬇️
Java SDK	60.14% <ø> (ø)
C# SDK	69.07% <ø> (-0.31%)	⬇️
Python SDK	81.43% <ø> (ø)
Node SDK	91.53% <ø> (ø)
Go SDK	39.43% <ø> (ø)

Files with missing lines	Coverage Δ
core/server/src/streaming/partitions/storage.rs	71.50% <100.00%> (+4.30%)	⬆️

... and 277 files with indirect coverage changes

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[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs.

If you need a review, please ensure CI is green and the PR is rebased on the latest master. Don't hesitate to ping the maintainers - either @core on Discord or by mentioning them directly here on the PR.

Thank you for your contribution!

[hubcio]

can you make it a integration test instead of unit? code in core/server will be replaced when we introduce clustering, thus test will be lost.

[atharvalade]

can you make it a integration test instead of unit? code in core/server will be replaced when we introduce clustering, thus test will be lost.

Good call, moved the tests from core/server unit tests to core/integration/tests/storage/consumer_offsets.rs. They follow the same pattern as tests/state/ (direct server:: imports, no full harness needed). This way they survive the server ti server-ng migration and can be re-run against the new binary.