DRU-493 - Drag board cards between statuses

[chaosk]

Summary

• Widen Cards with layout=stack and drop, and Card with drag, instead of a new Board block.
• The Software Factory board stacks one card per column. Dropping a card onto another column POSTs the existing set_status door and refreshes the page.
• Click still opens the ticket. Drop onto the same column does not POST. Ready for Agent still goes through Ticket.transition.

Test plan

• On the board, drag a Todo card onto In Progress. The card moves; the ticket page Status matches.
• Click a card (no drag). The ticket page opens.
• Drop a card onto its own column. Nothing changes.
• Drag onto Ready for Agent. At most one build starts.
• Field notes Cards (no drop) still wrap across the page.

Made with Cursor