Horsea's gates showed block_ddf/block_slot change real PTX in
BlockHaloCopy, BlockExplode and BlockExplodeProjected (6/10 modules;
BlockExplodeProjected 38 -> 40 registers) although the results stayed
exact. The stack's bar is byte-identical PTX for naming-only steps, so
those three kernels return to their K3 expressions, the helpers leave
core/layout.cuh, and test_projected_explosion goes back to its K3 form.
fill_invalid stays (its kernels were byte-identical). K4 vs K3 is now
only the NaN-fill helper.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
K4 made BlockExplodeProjected address storage through block_ddf and
block_slot (core/layout.cuh). This host test compiles the kernel text
extracted from blocks.cu, so it now also extracts those two helper
definitions from core/layout.cuh (device qualifiers -> inline) instead of
failing to compile. Assertions and tolerances unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>