observe
Installs the sole retained text observer used by a runtime text-area node.
This privileged bridge is not an application event API. The returned release operation is idempotent and confined to the execution owner. Releasing it does not release the caller-owned text or scroll state.
Return
an idempotent subscription release operation.
Parameters
callback
callback invoked synchronously after each distinct normalized write.
Throws
when called from another execution owner or while another text observer is live.