fix(buun-llama-cpp): match speculative draft split anchor

The shared gRPC wrapper stores p_split under the draft sub-structure. Match that exact source spelling so the fork-specific patch stage reaches the build on every architecture.

Assisted-by: Codex:gpt-5 [Codex]

backend/cpp/buun-llama-cpp/patch-grpc-server.sh

@@ -90,7 +90,7 @@ else
     awk '
         prev2 == "        } else if (!strcmp(optname, \"spec_p_split\")) {" &&
         prev1 ~ /^ +if \(optval != NULL\) \{$/ &&
-        $0    ~ /^ +try \{ params\.speculative\.p_split = std::stof\(optval_str\); \} catch \(\.\.\.\) \{\}$/ &&
+        $0    ~ /^ +try \{ params\.speculative\.draft\.p_split = std::stof\(optval_str\); \} catch \(\.\.\.\) \{\}$/ &&
         !done {
             print                        # print the try-line itself
             getline inner_close          # read "            }" closing the inner if