Engage flash SDPA in MHA/GQA causal-only path (#22910)

* Route MHA/GQA causal-only path through is_causal SDPA

* Skip causal-only fast path when _compute_attention is overridden

* Strengthen extra_mask coverage in causal-only fallback tests

Marcos Ashton committed 3mo ago

5a524001dbc89cc9be4e034da0ee7c5f8064aafd

Parent: c42b5ae

Committed by GitHub <noreply@github.com> on 5/27/2026, 8:38:49 PM