Function optimisticUndo

optimisticUndo(
    bus: CommandBus,
    actions: string[],
    options?: OptimisticUndoOptions,
): Plugin
Optimistic dispatch plugin that auto-rollbacks using the bus's registered undo handlers.

Unlike optimistic(), this plugin does not require separate apply/rollback closures — it uses the undo handler already registered via register(action, handler, { undo }).

How it works on an async bus:
1. Immediately returns { ok: true, value: predict(cmd) } to the caller.
2. The real handler runs in the background.
3. If the real handler fails, the registered undo handler is called automatically.
On a sync bus: behaves like the regular optimistic() — runs handler synchronously, rolls back via undo handler if it fails.

Requires undo handlers to be registered for the targeted actions. Actions without undo handlers are passed through unchanged.
Parameters
- bus: CommandBus
- actions: string[]
- options: OptimisticUndoOptions = {}
Returns Plugin
Example
```
bus.register('cartAdd', addToCart, { undo: removeFromCart });
bus.use(optimisticUndo(bus, ['cartAdd'], {
  predict: (cmd) => ({ id: cmd.target.id, qty: cmd.payload.qty }),
  onRollback: (cmd, err) => toast.error(`Failed to add item: ${err.message}`),
}));
// dispatch returns immediately with predicted result
const result = await bus.dispatch('cartAdd', { id: 5 }, { qty: 2 });
// result.ok === true, result.value === { id: 5, qty: 2 }
```
- Defined in plugins-core.ts:342