Update CHANGELOG.md

Update a project's CHANGELOG.md with relevant user-facing changes since the last versioned release.

Iron Laws

• ONLY USER-FACING CHANGES — internal refactors, CI config, test-only changes, and release bookkeeping do not belong in the changelog
• NEVER DUPLICATE — check the existing [Unreleased] section before adding entries
• DESCRIBE IMPACT, NOT IMPLEMENTATION — write what changed for the user, not what the commit did

Procedure

1. Find the baseline

Read CHANGELOG.md and identify the most recent versioned release heading (e.g., ## [0.5.1] - 2026-02-27). Extract the version tag (e.g., v0.5.1).

2. Gather commits since baseline