feat(muh): apply CCCL-derived BI-V100 tuning to 5 vllm Python files

Applied via muh/vllm_bi100_patch.py --conservative:

1. paged_attn.py: removed use_v1=True hardcode, restored V1/V2 heuristic
   with BI-V100 threshold (16384 vs default 8192). SM=16 favors V1 longer.

2. fused_moe.py: BLOCK_SIZE_K 32→64 (better memory coalescing with 900GB/s
   BW), BLOCK_SIZE_N 32→64 for decode path. Qwen3.6 MoE: E≈128, topk=8.

3. _custom_ops.py: SMEM kept at 32KB (conservative mode, pending hardware
   confirmation). Added diagnostic comment.

4. prefix_prefill.py: enhanced BI-V100 block config comment with SMEM
   budget breakdown (BLOCK=64,N=64 → 48KB tight, N=32 → 32KB safe).

5. triton_flash_attention.py: added 2 BI-V100 autotune configs
   (64x32 and 32x64) for SM=16 occupancy characteristics.

CCCL basis: cub/benchmarks/bench/ %RANGE% parameter spaces (reduce 1044
combos, scan 5.4M, topk 1698, transform 25920) → SMEM pruning → policy
selector logic from tuning_*.cuh.

Also includes muh/vllm_bi100_patch.py (713 lines) for reproducible
one-shot patching with --dry-run, --conservative, and --revert modes.

vllm/model_executor/layers/fused_moe/fused_moe.py

@@ -338,17 +338,23 @@ def get_default_config(
     dtype: Optional[str],
     is_marlin: bool,
 ) -> Dict[str, int]:
+    # muh: BI-V100 (SM=16, 48KB SMEM) aware defaults
+    # Qwen3.6 MoE: E≈128, topk=8, K≈2048, N≈5504
+    # SM=16 → fewer CTAs → each CTA should do more work → larger K tile
+    # SMEM check: M=64 * K=64 * 2B(fp16) * 2(A+B) = 16KB < 48KB ✓
     config = {
         'BLOCK_SIZE_M': 64,
         'BLOCK_SIZE_N': 64,
-        'BLOCK_SIZE_K': 32,
+        'BLOCK_SIZE_K': 64,   # muh: 32→64, better memory coalescing on BI-V100
         'GROUP_SIZE_M': 8
     }
     # A heuristic: fused marlin works faster with this config for small M
     if M <= E or (is_marlin and M <= 32):
+        # muh: decode path (M=1 for single-token, M=8 for topk=8)
+        # BI-V100: K=64 good for memory BW, N=64 for output tile
         config = {
             'BLOCK_SIZE_M': 16,
-            'BLOCK_SIZE_N': 32,
+            'BLOCK_SIZE_N': 64,   # muh: 32→64, wider output tile
             'BLOCK_SIZE_K': 64,
             'GROUP_SIZE_M': 1
         }