Parent-Task:

• SR-14113 Support _read and _modify accessor differentiation

relates to:

• TF-1078 [AD] Incorrect derivatives for coroutines (begin_apply for a modify accessor)

Issue Description:

Coroutine differentiation should be diagnosed until it is supported.

Currently, differentiation of active coroutine calls is not diagnosed and silently produces incorrect results: TF-1078.

This is because begin_apply is not handled in activity analysis or "should differentiate instruction" logic.