Buyer-script QA caught two regressions:
1. Toast on action failure leaked 'runtime-values isn't reachable' and
'Backend can't accept' — engineering jargon a buyer would read as
'product is broken'.
2. After a real 500, the button stayed enabled so a buyer could click
again into the same error.
Now:
- Failure toast says 'The runtime engine couldn't accept that decision.
Action buttons are now disabled until it recovers.' (no jargon, no
raw error strings).
- handleAction sets runtimeHealth='down' on the failure, which flips
the runtime-note banner on and disables every action button.
- Non-runtime failures get the even-shorter 'Something went wrong
handling that action. Try again in a moment.'
