server : support jinja extra template kwargs (Qwen3 enable_thinking feature), from command line and from client (ggml-org#13196)

* initial commit for handling extra template kwargs

* enable_thinking and assistant prefill cannot be enabled at the same time

* can set chat_template_kwargs in command line

* added doc

* fixed formatting

* add support for extra context in generic template init

* coding standard: common/chat.cpp

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* coding standard:  common/chat.cpp

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* Apply suggestions from code review

coding standard: cosmetic changes

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* fix merge conflict

* chat.cpp: simplify calls to apply to ensure systematic propagation of extra_context (+ the odd existing additional_context)

* normalize environment variable name

* simplify code

* prefill cannot be used with thinking models

* compatibility with the new reasoning-budget parameter

* fix prefill for non thinking models

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
Co-authored-by: Olivier Chafik <olivier.chafik@gmail.com>

Author: 3 people

common/common.h

@@ -8,6 +8,7 @@
 #include <string>
 #include <string_view>
 #include <vector>
+#include <map>
 #include <sstream>
 
 #ifdef _WIN32
@@ -381,6 +382,8 @@ struct common_params {
     std::string ssl_file_key  = "";                                                                         // NOLINT
     std::string ssl_file_cert = "";                                                                         // NOLINT
 
+    std::map<std::string, std::string> default_template_kwargs;
+
     // "advanced" endpoints are disabled by default for better security
     bool webui            = true;
     bool endpoint_slots   = false;

tools/server/server.cpp

@@ -2110,6 +2110,7 @@ struct server_context {
             /* use_jinja             */ params_base.use_jinja,
             /* prefill_assistant     */ params_base.prefill_assistant,
             /* reasoning_format      */ params_base.reasoning_format,
+            /* chat_template_kwargs  */ params_base.default_template_kwargs,
             /* common_chat_templates */ chat_templates.get(),
             /* allow_image           */ mctx ? mtmd_support_vision(mctx) : false,
             /* allow_audio           */ mctx ? mtmd_support_audio (mctx) : false,