Full Context on a Vulkan-Only Strix Halo: The Decode-Drop Reproduces, but the Sweet Spot Moves

kmarble showed ROCm decode collapses 64% at full context on Strix Halo, and ROCm+MTP cures it. My board can't run ROCm. The Vulkan half reproduces the drop — but the MTP sweet spot from last week walks left at depth: by 76k, drafting too deep is slower than no speculation at all.