Function action

src/components/messageActions.tsx:148–157

(a: {
  key: K;
  label: string | ((s: MessageActionsState) => string);
  types: readonly T[];
  applies?: (s: MessageActionsState) => boolean;
  stays?: true;
  run: (m: NavigableOf<T>, caps: MessageActionCaps) => void;
})

// Identity builder — preserves tuple type so `run`'s param narrows (array literal widens without this).
function action<const T extends NavigableType, const K extends string>(a: {
  key: K;
  label: string | ((s: MessageActionsState) => string);
  types: readonly T[];
  applies?: (s: MessageActionsState) => boolean;
  stays?: true;
  run: (m: NavigableOf<T>, caps: MessageActionCaps) => void;
}) {
  return a;
}
export const MESSAGE_ACTIONS = [action({
  key: 'enter',
  label: s => s.expanded ? 'collapse' : 'expand',