Refactor the completions system to support both CLI mode (via
`/__COMPLETIONS.json`) and a client-side fallback scan for dev mode.
- Implement client-side scanning of the file index for dice and headings
- Add `ensureCompletions` to allow components to await data readiness
- Update `JournalInput` to handle "no results" states in the dropdown
- Improve keyboard navigation (Tab to accept, Enter to select)
- Update dice regex to support `:md-dice[...]` syntax
hypercross