Sample A anchors and gather them into a faithful DFlash batch. Each anchor at
response position t contributes its full prefix context [0..t] (capped at
maxCtx, keeping the most recent), left-padded. The final tapped layer (last
in tapLayers = post-finalNorm) supplies the block's p^t hiddens.
Sample A anchors and gather them into a faithful DFlash batch. Each anchor at response position t contributes its full prefix context [0..t] (capped at maxCtx, keeping the most recent), left-padded. The final tapped layer (last in tapLayers = post-finalNorm) supplies the block's p^t hiddens.