ci: send each version's changelog to the comfy registry

The registry's Updates section was empty for every version because the
publish workflow never passed a changelog. comfy-cli reads
COMFY_NODE_CHANGELOG, so the workflow now builds it from the version's
CHANGELOG.md section. The registry shows it as one plain paragraph (no
Markdown), so the script keeps the first column of each table row.

Releases also date that CHANGELOG section and get an annotated vX.Y.Z
tag; CLAUDE.md and /version-bump describe the steps.

.github/workflows/publish.yml

@@ -19,6 +19,14 @@ jobs:
     steps:
       - name: Check out code
         uses: actions/checkout@v4
+      # comfy-cli sends $COMFY_NODE_CHANGELOG as the version's changelog (the registry's "Updates" section)
+      - name: Build registry changelog from CHANGELOG.md
+        run: |
+          {
+            echo "COMFY_NODE_CHANGELOG<<CHANGELOG_EOF"
+            python3 .github/scripts/registry_changelog.py
+            echo "CHANGELOG_EOF"
+          } >> "$GITHUB_ENV"
       - name: Publish Custom Node
         uses: Comfy-Org/publish-node-action@v1
         with: