Changelog fragments

Each user-facing change ships as one file here instead of editing CHANGELOG.md directly, so concurrent pull requests never conflict.

Name the file <PR number>.<type>.md, where <type> is one of added, changed, deprecated, removed, fixed, or security. A second fragment for the same PR and type takes a counter suffix: 1234.fixed.2.md. Add the fragment after opening the PR, when its number is known.

Write the entry as a single line without a bullet or PR link; towncrier adds the link from the filename. Prefix **Breaking:** for changes that bump the major version.

Release a minor version for any ready backward-compatible improvement and a patch for backward-compatible fixes; there is no minimum release size.

To release version X.Y.Z:

1. Run uv run towncrier build --yes --version X.Y.Z.
2. Commit the updated changelog and deleted fragments, then tag that commit.

Pushing the tag publishes to PyPI and creates the GitHub release from the matching CHANGELOG.md section.