- Add hf calendar command group to command surface and router
- Implement schedule/show/edit/cancel/date-list commands
- Implement plan-schedule/plan-list/plan-edit/plan-cancel commands
- Add leaf help for all calendar commands
- Align CLI with backend calendar routes and response envelopes
- Support virtual slot ids for edit/cancel
- Validate with go build and go test ./...
- 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
