Bug: event handlers in fragment roots

[frolic]

React version: 19.0.0

Steps To Reproduce

1. Use createRoot with a document fragment instead of element
2. Notice how none of the onFocus, onClick, onSubmit, etc. event handlers don't work

Link to code example:
https://codesandbox.io/p/sandbox/wonderful-tristan-lxwl5d

(Note that this uses the flushSync-before-append approach in #25101 (comment), but unclear if that's related to how events are bound.)

The current behavior

All event handlers bound with on* props inside the React root rendered to a document fragment don't seem to work. This can be worked around with refs and setting up event listeners.

The expected behavior

I would expect on* props to work the same as React roots rendered to elements.