fix: Add changelog fragment to auto-updater script

The update-package.sh script now generates a changelog fragment
so auto-update PRs pass the towncrier check CI step.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: anth-volk

.github/scripts/update-package.sh

@@ -58,10 +58,14 @@ if git diff --quiet uv.lock pyproject.toml; then
   exit 0
 fi
 
-# 7. Create branch, commit, push, open PR
+# 7. Create branch, add changelog fragment, commit, push, open PR
 BRANCH="auto/update-${PACKAGE}-${LATEST}"
 git checkout -b "$BRANCH"
-git add uv.lock pyproject.toml
+
+FRAGMENT="changelog.d/${PACKAGE}-${LATEST}.changed.md"
+echo "Update ${PACKAGE} to ${LATEST}." > "$FRAGMENT"
+
+git add uv.lock pyproject.toml "$FRAGMENT"
 git commit -m "chore(deps): update ${PACKAGE} to ${LATEST}"
 git push -u origin "$BRANCH"
 

changelog.d/147.fixed.md

@@ -0,0 +1 @@
+Auto-updater PRs now include a changelog fragment.