[Perf] (MG_Backend): give DirectVulkan's draw memo a table that fits in cache lines

The per-VAO resolved-bindings map probe was ~45% of
UploadAndBindVertexBuffers' self time, and the aux-memo pointer chase
was the single hottest instruction left in TrySetupDrawFastPath. Both
die together: a fixed 2048-slot two-probe 64B-aligned VaoDrawMemo table
embeds the VAO key, content-hash-validated layout facts and the
bindings payload reordered hot-to-cold. Layout facts hold exactly while
the slot's content hash equals the live VAO's own config-guarded hash;
a recycled VAO address either misses or reproduces a byte-identical
config, for which the facts are correct by construction. Bindings keep
their full per-draw revalidation; recycled slots zero their frame
serials so half-filled entries can never match.

ComputePipelineStateHash, the depth/stencil probe and the
primitive-restart probe now take one bulk GetRenderStateParameters()
fetch instead of ~17 cross-TU accessor calls (verified pure field
reads, identical bit packing). The EBO slice memo gained the same
manager-wide epoch one-compare rescue the vertex half uses.
GetShaderTransformFlags is memoized on pre-transform. Sodium's
MultiDrawElementsBaseVertex hoists GetGLTypeSize out of the
per-sub-draw loop, replaces the division with a shift, and skips
unsupported index types loudly instead of dividing by zero.

Also verified: a GL_BLEND toggle recompiles nothing in steady state -
the glslang frames in earlier state_toggle profiles were startup
contamination.

Quiet-box load-gated 6-round A/B: sodium_multidraw -8.0%, tex_param
-4.1%, use_program -3.3%; steady-state vanilla_draw CPU -20% ns/op at
4096 frames (the 80-frame matrix compresses CPU wins under GPU boost
clocks; profiles confirm UploadAndBindVertexBuffers 6.3% -> 4.4%
including the table probe, and the aux cold-line load gone). The one
matrix flag (pass_switch +7.5%) reversed to -3.2% in 10-pair isolated
re-runs. Unit tests 421/421.

MobileGL/MG_Backend/DirectVulkan/DirectVulkan.cpp

@@ -16,6 +16,7 @@
 #include "MG_Util/Metrics/TextureMetrics.h"
 #include "MG_Util/Miscellany/IndexGenerator.h"
 #include <atomic>
+#include <bit>
 #include <cstring>
 #include <spirv_reflect.h>
 
@@ -1450,6 +1451,18 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         payload.mode = mode;
         payload.indexBufferView.indexType = type;
 
+        // Loop-invariant: the index type is fixed for the whole multi-draw, so resolve
+        // its byte size once instead of twice per sub-draw (a cross-TU switch that
+        // showed up in per-frame profiles of sodium-style 132x32 multi-draws). Index
+        // sizes are 1/2/4, so the per-sub-draw offset division below reduces to a
+        // shift - the hardware divide was the hottest instruction of this loop.
+        const SizeT indexSize = MG_Util::GetGLTypeSize(type);
+        if (indexSize == 0) {
+            MGLOG_E("MultiDrawElementsBaseVertex skipped: unsupported index type 0x%x", type);
+            return;
+        }
+        const Uint32 indexSizeShift = static_cast<Uint32>(std::countr_zero(indexSize));
+
         // TODO: allocate draw cmd buf elsewhere
         static Vector<DrawIndexedCmdParam> params;
         params.clear();
@@ -1464,14 +1477,14 @@ namespace MobileGL::MG_Backend::DirectVulkan {
 
             payload.indexBufferView.indexByteOffset = 0;
             payload.indexBufferView.indexByteSize =
-                    std::max(reinterpret_cast<SizeT>(indices[i]) + count[i] * MG_Util::GetGLTypeSize(type),
+                    std::max(reinterpret_cast<SizeT>(indices[i]) + count[i] * indexSize,
                              payload.indexBufferView.indexByteSize);
 
             auto& param = params[i];
 
             param.indexCount = count[i];
             param.instanceCount = 1;
-            param.firstIndex = reinterpret_cast<SizeT>(indices[i]) / MG_Util::GetGLTypeSize(type);
+            param.firstIndex = reinterpret_cast<SizeT>(indices[i]) >> indexSizeShift;
             param.vertexOffset = basevertex[i];
             param.firstInstance = 0;
         }