chore: import upstream snapshot with attribution

tools/server/server-chat.h

@@ -0,0 +1,26 @@
+// Chat conversion functions for server (Responses API, Anthropic API, OAI streaming diffs)
+
+#pragma once
+
+#include "chat.h"
+#include "server-common.h"
+#include "server-http.h"
+
+#include <nlohmann/json_fwd.hpp>
+
+using json = nlohmann::ordered_json;
+
+// Convert OpenAI Responses API format to OpenAI Chat Completions API format
+json server_chat_convert_responses_to_chatcmpl(const json & body);
+
+// Convert Anthropic Messages API format to OpenAI Chat Completions API format
+json server_chat_convert_anthropic_to_oai(const json & body);
+
+// convert OpenAI transcriptions API format to OpenAI Chat Completions API format
+json convert_transcriptions_to_chatcmpl(
+    const json & body,
+    const common_chat_templates * tmpls,
+    const std::map<std::string, uploaded_file> & in_files,
+    std::vector<raw_buffer> & out_files);
+
+json server_chat_msg_diff_to_json_oaicompat(const common_chat_msg_diff & diff);