feat(ci): extract changelog generation script and use for draft releases

- Create script/generate-changelog.ts with reusable changelog generation logic
- Update ci.yml draft-release job to use the new script instead of GitHub's generate-notes API
- Ensures draft release notes follow the same format as published releases

🤖 Generated with assistance of oh-my-opencode

.github/workflows/ci.yml

@@ -79,26 +79,16 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Get latest published release tag
-        id: latest-release
-        run: |
-          LATEST_TAG=$(gh release list --exclude-drafts --exclude-pre-releases --limit 1 --json tagName --jq '.[0].tagName // empty')
-          echo "tag=${LATEST_TAG}" >> $GITHUB_OUTPUT
-          echo "Latest published release: ${LATEST_TAG:-none}"
-        env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      - run: git fetch --force --tags
+
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
 
       - name: Generate release notes
         id: notes
         run: |
-          if [ -n "${{ steps.latest-release.outputs.tag }}" ]; then
-            NOTES=$(gh api repos/${{ github.repository }}/releases/generate-notes \
-              -f tag_name=next \
-              -f previous_tag_name=${{ steps.latest-release.outputs.tag }} \
-              --jq '.body')
-          else
-            NOTES="Initial release"
-          fi
+          NOTES=$(bun run script/generate-changelog.ts)
           echo "notes<<EOF" >> $GITHUB_OUTPUT
           echo "$NOTES" >> $GITHUB_OUTPUT
           echo "EOF" >> $GITHUB_OUTPUT