Declare open-gen-ui and open-gen-ui-advanced in langgraph-python
manifest (code existed, was never registered). Add both to
constrained-explicit allowlist, fill shell_docs_path for 5 demos,
add hitl-in-app override, drop stale chat-customization-css fallback.
Regenerate registry.json, demo-content.json, constraints.json,
and docs-status.json across shell / shell-dojo / shell-docs.
Bump feature/demo count assertion 30→32 in generate-registry test.
Extend check-binaries.sh whitelist for sister-shell demo-content.