Unbreak the release build's metadata check

[jessegrabowski]

Every release build has failed for the past week, v0.2.0 included, so that version never reached PyPI. Hatchling now emits Metadata-Version: 2.5 and the twine pinned inside build-and-inspect-python-package v2.18.0 rejects it as invalid. v3.0.1 of the action ships twine 7, which accepts it.

Also swapped the deprecated license = {file = ...} table for a PEP 639 expression, so the metadata carries License-Expression: Apache-2.0 rather than the full 11KB of license text inlined into the License: field.

Verified locally: twine 6 reproduces the CI error on a fresh build, twine 7 passes check --strict on both the sdist and the wheel.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.52%. Comparing base (85ebae4) to head (6819084).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #110   +/-   ##
=======================================
  Coverage   97.52%   97.52%           
=======================================
  Files          61       61           
  Lines        3076     3076           
=======================================
  Hits         3000     3000           
  Misses         76       76           

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