Native create forms on macOS

Every "create" flow in the Cmd+K command palette now opens a native macOS form rather than a web dialog. They feel like the system: native fields, per-view styling, file and directory pickers, and a confirm step for destructive actions.

The full set is covered: notes, tasks, email, calendar events, channels, direct messages, sheets, slides, repos, routines, and apps. Async fields (like picking a parent folder) load their options natively as you go.