* "Uncooperative cards" is now a warning.
* Cards and actions get "Then" invoked before the card processor considers erroring out.
* Terminal UI: Errors and warnings from actions are displayed during the response; they're not only added to the temporary messages now.
Only cards can block other cards or actions from being used due to urgency, so only display the `[URGENT!]` header for cards. Debug actions can't be blocked, so skip the "urgency conflict" check for those.
Fixes some off-by-one errors. A 1-indexed UI in a 0-indexed language is always going to be prone to those and I will no doubt find more when I have enough of a test program to experiment with...
