CI artifacts missing in some jobs

[marco66colombo]

Prerequisites

Please make sure to check off these prerequisites before submitting a bug report.

• Test that the bug appears on the current version of the master branch. Make sure to include the commit hash of the commit you checked out.
• Check that the issue hasn't already been reported, by checking the currently open issues.
• If there are steps to reproduce the problem, make sure to write them down below.
• If relevant, please include the hls4ml project files, which were created directly before and/or after the bug.

Quick summary

Some CI jobs upload no artifacts even though the CI template expects tarballs and/or synthesis reports, which results in artifact upload warnings. The jobs do not fail, but this is noisy.

Details

Steps to Reproduce

1. Look at a CI job that only executes tests without synthesis and without explicit tarball generation, e.g.
   • test_recurrent_pytorch.py::test_gru, test_lstm, test_rnn
   • https://gitlab.cern.ch/fastmachinelearning/hls4ml/-/jobs/69760179
2. Observe the artifact upload step.

Expected behavior

Artifacts should be produced.

Actual behavior

Artifacts are produced only for certain backends/tests (e.g., Catapult where tarballs are always generated). Other jobs produce none and the upload step logs:

Uploading artifacts...
WARNING: test/pytest/*.tar.gz: no matching files...
WARNING: test/pytest/synthesis_report_*.json: no matching files...
ERROR: No files to upload

Optional

Possible fix

• Add a WriteTar configuration to CatapultWriter for consistency with other backends.
• If artifacts are desired, update tests to set write_tar=True.

Additional context

The root cause is inconsistent artifact production: Catapult always generates .tar.gz archives (unconditional write_tar in CatapultWriter.write_hls()), while other backends only generate tarballs when WriterConfig.WriteTar is enabled (default False).

Evidence

• hls4ml/writer/catapult_writer.py: write_hls() always calls self.write_tar(model) (no config gate).
• hls4ml/writer/vivado_writer.py, oneapi_writer.py, quartus_writer.py: tarball creation is gated by WriteTar.