loosen up the regex and grammar around tool calls

Author: aldehir

common/chat.cpp

@@ -1326,7 +1326,7 @@ static common_chat_params common_chat_params_init_gpt_oss(const common_chat_temp
                 builder.resolve_refs(parameters);
 
                 tool_rules.push_back(builder.add_rule(name + "-call",
-                    "\"" + name + "\"" + " space? \"<|constrain|>json<|message|>\" " + builder.add_schema(name + "-args", parameters)
+                    "\"" + name + "\"" + " space* \"<|constrain|>\"? \"json<|message|>\" " + builder.add_schema(name + "-args", parameters)
                 ));
             });
 
@@ -1343,6 +1343,7 @@ static common_chat_params common_chat_params_init_gpt_oss(const common_chat_temp
                 "<|constrain|>",
                 "<|message|>",
                 "<|start|>",
+                "<|end|>",
             };
         });
     }
@@ -1358,7 +1359,7 @@ static void common_chat_parse_gpt_oss(common_chat_msg_parser & builder) {
     static const common_regex to_regex(" to=");
     static const common_regex channel_type_regexp("(final|analysis|commentary)");
     static const common_regex user_tool_call_regex(
-        "functions\\.([a-zA-Z_][a-zA-Z0-9_]*)\\s?(?:<\\|constrain\\|>([a-zA-Z]+))?<\\|message\\|>"
+        "functions\\.([a-zA-Z_][a-zA-Z0-9_]*)\\s*(?:(?:<\\|constrain\\|>)?([a-zA-Z]+))?\\s*<\\|message\\|>"
     );
     static const common_regex builtin_tool_call_regex("(?:browser|python)[\\s\\S]*<\\|message\\|>");