fix: disable semantic-release changelog and restore GitHub release assets upload step

[farhan]

Summary

Team decided:

1. not to configure a CHANGELOG.rst with semantic-release.
2. re-aligns release.yml to the recommended sample-plugin release.yml, whose release flow is confirmed working.

Changes

Commit 1 — revert #70 (disable changelog):

• Restore changelog: "false" on the Run Semantic Release step in release.yml.
• Remove the [tool.semantic_release.changelog] config from pyproject.toml.
• Delete CHANGELOG.rst.

Commit 2 — restore the release-assets step:

• Re-add the python-semantic-release/publish-action "Upload to GitHub Release Assets" step (removed in 3a9f71e), placed right after the Run Semantic Release step, matching the client's sample-plugin.

Net result

Changelog generation disabled and the GitHub release assets upload step restored

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.17%. Comparing base (b183eff) to head (72b7d65).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #71   +/-   ##
=======================================
  Coverage   82.17%   82.17%           
=======================================
  Files          48       48           
  Lines        1419     1419           
  Branches      110      110           
=======================================
  Hits         1166     1166           
  Misses        221      221           
  Partials       32       32           

Flag	Coverage Δ
unittests	82.17% <ø> (ø)

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