common/parser: add --skip-chat-parsing to force a pure content parser. (#20289)

* Add `--force-pure-content` to force a pure content parser.

* Update common/arg.cpp

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* Change parameter name [no ci]

---------

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

tools/server/server-common.cpp

@@ -1065,6 +1065,7 @@ json oaicompat_chat_params_parse(
 
         inputs.add_generation_prompt = true;
     }
+    inputs.force_pure_content = opt.force_pure_content;
 
     // Apply chat template to the list of messages
     auto chat_params = common_chat_templates_apply(opt.tmpls.get(), inputs);

tools/server/server-common.h

@@ -290,6 +290,7 @@ struct server_chat_params {
     int  reasoning_budget = -1;
     std::string reasoning_budget_message;
     std::string media_path;
+    bool force_pure_content = false;
 };
 
 // used by /completions endpoint

tools/server/server-context.cpp

@@ -911,6 +911,7 @@ private:
                 /* reasoning_budget      */ params_base.reasoning_budget,
                 /* reasoning_budget_msg  */ params_base.reasoning_budget_message,
                 /* media_path            */ params_base.media_path,
+                /* force_pure_content    */ params_base.force_pure_content_parser
             };
         }