Each column gets its own form at the bottom (styled like the sidebar
inbox's), creating the card directly in that status, appended after
its existing cards.
- API: POST /projects/{id}/cards takes an optional status_id, which
must belong to the project (422 otherwise); omitted, it still
defaults to the project's first status as before. Position is
already "end of that status" for free -- createInProject() already
ranks by (owner, project, status).
- cards store: add() takes an optional statusId, forwarded as
status_id when given.
- ProjectView: one draft string per status (keyed by status id) so
typing in one column doesn't touch another's, mirroring the
per-status independence the columns already have for reordering.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>