recipe(deepseek-v4-flash-eugr): second-variant test config

- kv-cache-memory-bytes 20GB -> 21.47GB (21 GiB)
- max-model-len 1M -> 512K
- reasoning_effort=high -> max
- enable VLLM_DSV4_REASONING_CONTENT=1 (read reasoning_content key in the
  vendored tokenizer; the patch is baked in and gated by this env var)

Complements the reasoning_effort minimal patch + the default-off
reasoning_content patcher. This is the 'second variant' config.

recipes/deepseek-v4-flash-eugr/recipe.toml

@@ -49,10 +49,10 @@ entrypoint = ["vllm", "serve"]
 
 args = [
     "--kv-cache-dtype", "fp8",
-    "--kv-cache-memory-bytes", "20000000000",
+    "--kv-cache-memory-bytes", "21474836480",
     "--block-size", "256",
     "--load-format", "instanttensor",
-    "--max-model-len", "1048576",
+    "--max-model-len", "524288",
     "--max-num-seqs", "8",
     "--max-num-batched-tokens", "8192",
     "--max-cudagraph-capture-size", "64",
@@ -89,7 +89,7 @@ args = [
     "--enable-auto-tool-choice",
     "--generation-config", "vllm",
     "--default-chat-template-kwargs.thinking=true",
-    "--default-chat-template-kwargs.reasoning_effort=high",
+    "--default-chat-template-kwargs.reasoning_effort=max",
     "--disable-custom-all-reduce",
     "--trust-remote-code",
 ]
@@ -142,3 +142,5 @@ NCCL_SOCKET_FAMILY = "inet"
 # PCIe allreduce not needed on GB10 single-NIC
 VLLM_ENABLE_PCIE_ALLREDUCE = "0"
 VLLM_PCIE_ALLREDUCE_BACKEND = "cpp"
+
+VLLM_DSV4_REASONING_CONTENT = "1"