Automate version bumping in CI/CD pipeline

[baogorek]

Problem

Version bumping is currently manual and error-prone. The recent 0.5.0 release was delayed because:

1. make changelog includes bump-version changelog.yaml pyproject.toml but this step either wasn't run or failed silently
2. CHANGELOG.md was updated to show 0.5.0, but pyproject.toml still had 0.4.3
3. CI's skip-existing: true silently skipped publishing since 0.4.3 already existed on PyPI
4. The weight distribution diagnostics feature (PR Add weight distribution diagnostics and use_gates option #35) was merged but never published

Current Workflow

Manual steps required before pushing to main:

1. Add entry to changelog_entry.yaml
2. Run make changelog
3. Verify pyproject.toml was updated
4. Commit and push

Proposed Solution

Automate version bumping in the CI pipeline so that:

• When a PR is merged with a changelog_entry.yaml file, CI automatically runs the changelog/version bump
• Or: Add a pre-push hook or CI check that fails if changelog.yaml has unpublished bumps

Options to consider:

1. GitHub Action for changelog: Run make changelog in CI before the publish step
2. Pre-commit hook: Validate that versions are in sync before allowing commits
3. CI version check: Fail the build if changelog.yaml bump directives don't match pyproject.toml

Additional Note

l0/__init__.py has __version__ which was also out of sync (showed 0.1.0). Consider either:

• Removing it and reading version from importlib.metadata
• Including it in the bump-version command