Fix wheel builds not containing any src/ files

[solidDoWant]

Clean wheel builds (rm -rf dist/ OpenArc.egg-info/ build/ && uv build --wheel --no-sources) currently contain no actual project files, just metadata:

$ du -h dist/openarc-2.0.5-py3-none-any.whl 
8.0K    dist/openarc-2.0.5-py3-none-any.whl
$ unzip -l dist/openarc-2.0.5-py3-none-any.whl 
Archive:  dist/openarc-2.0.5-py3-none-any.whl
  Length      Date    Time    Name
---------  ---------- -----   ----
    11357  2026-05-22 19:44   openarc-2.0.5.dist-info/licenses/LICENSE
        0  2026-05-18 18:03   src/__init__.py
     5330  2026-05-22 19:44   openarc-2.0.5.dist-info/METADATA
       91  2026-05-22 19:44   openarc-2.0.5.dist-info/WHEEL
       40  2026-05-22 19:44   openarc-2.0.5.dist-info/entry_points.txt
        4  2026-05-22 19:44   openarc-2.0.5.dist-info/top_level.txt
      559  2026-05-22 19:44   openarc-2.0.5.dist-info/RECORD
---------                     -------
    17381                     7 files

This fixes the project config to include modules under src/:

$ du -h dist/openarc-2.0.5-py3-none-any.whl 
135K    dist/openarc-2.0.5-py3-none-any.whl

I also added a couple of missing items to .gitignore.

[SearchSavior]

Hey, can you give some context about what problem this change solves and what motivated the fix? I understand that the build wheel was empty, but why do you need to build a wheel in the first place?

[solidDoWant]

I'm building my own openarc images using a very different approach compared to the dockerfile for this project. This approach requires producing wheels, whose contents make up dockerfile layers. I'm also heavily considering using openarc as an in-process dependency (rather than a separate service) for a project I'm working on, which would have similar build requirements.