fix: max-num-seqs=1 + pure Q-tiling — match a3c45d3b exactly

Profiling hung for 30min then failed. Two causes:
1. max-num-seqs=2 (a3c45d3b used 1) — doubles profiling memory
2. flash_attn_varlen_func added to xformers patch — a3c45d3b had none

Restored:
- yaml: max-num-seqs=1 (exact a3c45d3b)
- patch_xformers_sdpa_seq.py: pure Q-tiling (exact a3c45d3b)

Only diff from a3c45d3b:
- yaml: BI100_MOE_COREX_TOPK_SOFTMAX=1 (was 0)
- protocol.py: extra=allow
- qwen3_5.py: corex_gdn_chunk_recurrent + corex_moe_index_combine imports
- prebuilt: 14 .so (was 13)

computility-run.yaml

@@ -15,7 +15,7 @@ command:
     - -tp
     - '4'
     - --max-num-seqs
-    - '2'
+    - '1'
     - --disable-log-requests
     - --disable-frontend-multiprocessing
     - --max-num-batched-tokens