Completes the preceding empty-rename commit: the getting-help "Hints"
section — F1 for a tier-3 teaching hint on the live input, `hint` to
explain the most recent error — with the real rendered block and a cast
showing both (the live-input hint via the demo-mode Ctrl-G→[F1] alias,
since autocast can't send F1, then `hint` on an error). the-assistive-editor
points at F1; CtrlG added to the cast generator's key map.
claude@clouddev1
028d32420d