engine: this GPU's own arithmetic and shared weight tiles as the builders' defaults

- layer_m.comp builds relaxed by default (M_RELAXED: f32 accumulators, paired FP8
  conversions, no activation table) with two windows per wave sharing weight tiles
  (WPW=2); M_EXACT=1 keeps NVIDIA's roundings, bit-identical to the CUDA path
- layer.comp reuses weight tiles across its waves (TPW=2 in the 32-channel layers)
- engine/rr/rr2_w.comp: one wave per window for preset F's dec0_0 and enc0, used by
  compile_rr2.py at the new default D4R_RR_RELAXED=3 (build_native_model.sh too);
  D4R_RR_FUSE=1 matches the reference's fused multiply-adds, ptx2rr.py --snorm16
- [Engine] Network defaults to vulkan; the HIP network is opt-in

config/d4r.ini.default

@@ -126,11 +126,10 @@ Enabled = false
 ; puts D4R_ENGINE_MODEL. The other folders: D4R_ENGINE_MODEL_LDR_DIR, D4R_ENGINE_MODEL_M_DIR,
 ; D4R_ENGINE_MODEL_M_LDR_DIR, D4R_ENGINE_MODEL_L_DIR and D4R_ENGINE_MODEL_L_LDR_DIR. (D4R_ENGINE_MODEL_DIR)
 ModelDir = auto
-; Where the network between the engine's Vulkan stages runs (K and M). hip = d4r's native HIP layer kernels
-; (M: about 1.7x faster than the shader, 3.8 instead of 5.5 ms per frame at 1080p -> 4K on an RX 9070 XT);
-; the game's command list is split around the network like a split frame, so it needs VkD3DDir, the CUDA
-; bridge and a model built with --hip. vulkan = the engine's cooperative-matrix shader, everything in one
-; command list. auto and hip = hip when available, else vulkan (the log says why). (D4R_ENGINE_NETWORK)
+; Where the network between the engine's Vulkan stages runs (K and M). vulkan = the engine's cooperative-matrix
+; shader, everything in one command list. hip = d4r's native HIP layer kernels: the game's command list is split
+; around the network like a split frame, so it needs VkD3DDir, the CUDA bridge and a model built with --hip; when
+; they are missing the Vulkan network runs and the log says why. auto = vulkan. (D4R_ENGINE_NETWORK)
 Network = auto
 
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