Function interactive_create 

pub fn interactive_create(
    mana_dir: &Path,
    prefill: Prefill,
) -> Result<CreateArgs>

Run the interactive unit creation wizard.

Prompts the user step-by-step for unit fields. Any field already provided in prefill is skipped (shown as pre-accepted).

Flow:

1. Title (required)
2. Parent (fuzzy-search from existing units, or none)
3. Verify command (with smart default from project type)
4. Acceptance criteria
5. Priority (P0-P4, default P2)
6. Description (open $EDITOR)
7. Produces / Requires (for dependency tracking)
8. Labels
9. Summary + confirm

Returns a fully populated CreateArgs.