gqa(ddd): add Detailed Design Document for GQA fused attention (ADR-0060)
Implementation-ready companion: file plan, DPPolicy placement, concrete
greenlet-tl kernel pseudocode for all 4 cases, integration points for
ADR-0061/62/63, 6-phase test-first plan, verification plan, perf model,
and an Open Decisions section recording autonomous choices for review
(greenlet-vs-composite, tree topology, batched dot, arena split, ghost
ADRs 0055-0059, numbering, bf16-as-f16).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
ywkang
fb600b3cdd