- Rename 'propose' group to 'proposal' in surface, leaf help, and routing
- Keep 'hf propose' as backward-compatible alias via groupAliases
- Add essential subcommand group: list, create, update, delete
- Accept command now shows generated story tasks in output
- Accept command supports --json output
- Task create blocks story/* types with helpful error message
- All help text updated to use 'proposal' terminology
