engine: presets E/F AutoExposure, the game's exposure fields and NGX's jitter order

NGX's CNN takes this frame's exposure scale and pre-exposure in both translated kernels (input words 244-256,
reconstruction 592-604) and the previous frame's exposure as the input kernel's texture 352
(cuda_copy_exposure_kernel's half surface). The runtime left all of it at the model dump's values, so HDR games
with a pre-exposure other than 1 or a changing exposure measured 18-39 dB against NGX; now 54-64 dB.

AutoExposure (flag 0x40), which the shim refused for E/F: NGX runs K's log-mean measurement on M's grid every
second frame. exposure_k.comp MODE 3 writes it to the 1x1 image the kernels sample; sr/exposure_copy_e.comp
keeps the previous exposure. 60-66 dB over eleven frames at 960x540 -> 1920x1080, pre-exposure 19-21.

The reconstruction's jitter words 544-556 are (y, x); the runtime wrote (-x, -y), which matches only the
harness's first three jitters, so every later frame of a game's jitter sequence measured 26-28 dB. Twelve-frame
captures now measure 60-66 dB HDR and LDR; on the Steam Deck through the shim 51-67 dB against ZLUDA.

The D3D12 harness takes per-frame lists in D4R_HARNESS_PRE_EXPOSURE / _EXPOSURE_SCALE; d4r-e takes the
AutoExposure flag, per-frame exposure values and the game's exposure texture. E/F models need rebuilding
(the install's model cache key changes); older models keep the old binding and refuse AutoExposure.

engine/sr/exposure_copy_e.comp

@@ -0,0 +1,20 @@
+#version 460
+// d4r engine, presets E and F: NGX's cuda_copy_exposure_kernel. After each frame the frame's exposure (the game's
+// 1x1 texture or the AutoExposure measurement) goes into a 1x1 half surface, which the next frame's input kernel
+// samples as the previous exposure (its texture 352; on a reset frame NGX binds the current exposure there instead,
+// so the engine copies before the input kernel too). The formatted half store truncates toward zero, like the
+// auto-exposure copy (engine/exposure_k.comp).
+layout(local_size_x = 32) in;   // one full wave32 subgroup; invocation 0 stores
+layout(set = 0, binding = 0) uniform sampler2D source;
+layout(set = 0, binding = 1, r16f) uniform writeonly image2D previous;
+float truncatedHalf(float v)
+{
+    uint bits = packHalf2x16(vec2(v, 0.0)) & 65535u;
+    if (unpackHalf2x16(bits).x > v) --bits;
+    return unpackHalf2x16(bits).x;
+}
+void main()
+{
+    if (gl_LocalInvocationID.x == 0u)
+        imageStore(previous, ivec2(0), vec4(truncatedHalf(texelFetch(source, ivec2(0), 0).r)));
+}