Unify CHANGES.md style for 1.3.1 section

Convert mxenv refactoring entries to match existing changelog style:
- Use simple bullets with prefixes (Fix, Feature, Breaking, Improvement)
- Remove subsections for consistent formatting

Author: jensens

CHANGES.md

@@ -6,33 +6,23 @@
 - Fix: interactive uv venv, use --allow-existing instead.
 - Feature: Add support for Python 3.14.
 - Feature: Add `docs-linkcheck` to check for broken links in the sphinx documentation.
-
-### Breaking Changes - mxenv domain refactoring
-
-- **Removed**: `MXENV_UV_GLOBAL` setting in favor of automatic UV detection.
+- Breaking: Removed `MXENV_UV_GLOBAL` setting in favor of automatic UV detection.
   When `PYTHON_PACKAGE_INSTALLER=uv`, mxmake now automatically detects and uses
   a globally installed `uv` if available. To force local installation of uv,
   simply don't install it globally or remove it from PATH.
-
-### New Features - mxenv domain
-
-- **Added**: `UV_PYTHON` setting to specify Python version for UV-managed virtual
+- Feature: Add `UV_PYTHON` setting to specify Python version for UV-managed virtual
   environments. Defaults to `PRIMARY_PYTHON` for backward compatibility. This
   provides semantic clarity: `PRIMARY_PYTHON` is the system interpreter path
   (e.g., `python3.11`), while `UV_PYTHON` is the version spec for UV
   (e.g., `3.14`, `[email protected]`).
-
-- **Added**: Automatic detection of global UV installation using simple shell check.
+- Feature: Automatic detection of global UV installation using simple shell check.
   No manual configuration required.
-
-- **Added**: All UV commands now run with `--quiet --no-progress` flags for better
+- Feature: All UV commands now run with `--quiet --no-progress` flags for better
   CI/CD compatibility and cleaner log output.
-
-- **Added**: When using global UV, mxmake checks if updates are available using
+- Feature: When using global UV, mxmake checks if updates are available using
   `uv self update --dry-run` and displays a helpful non-blocking warning if a
   newer version is available.
-
-- **Improved**: Simplified mxenv.mk logic from 3+ nesting levels to 1-2 levels
+- Improvement: Simplified mxenv.mk logic from 3+ nesting levels to 1-2 levels
   using computed intermediate variables (`USE_GLOBAL_UV`, `USE_LOCAL_UV`).
   Code is now more maintainable and easier to extend.