common : fix reasoning before forced tool call via tool_choice = required (#16264)

* common : fix reasoning before forced tool call via tool_choice = required

* common : improve reasoning and commentary handling when tool_choice is required

(cherry picked from commit c746984956d6882c2de73d53ae2bb3bdf889e475)

---------

Co-authored-by: Alde Rojas <hello@alde.dev>

common/chat.cpp

@@ -1616,17 +1616,36 @@ static common_chat_params common_chat_params_init_gpt_oss(const common_chat_temp
                 );
             });
 
-            auto recipient_in_role = builder.add_rule("recipient_in_role",
-                "\"<|start|>assistant\"? \" to=functions.\" ( " +
-                string_join(tool_rules_recipient_in_role, " | ") + " )"
-            );
-
             auto recipient_in_channel = builder.add_rule("recipient_in_channel",
                 channel + " \" to=functions.\" ( " +
                 string_join(tool_rules_recipient_in_channel, " | ") + " )"
             );
 
-            builder.add_rule("root", recipient_in_role + " | " + recipient_in_channel);
+            if (data.grammar_lazy) {
+                auto recipient_in_role = builder.add_rule("recipient_in_role",
+                    "\"<|start|>assistant\"? \" to=functions.\" ( " +
+                    string_join(tool_rules_recipient_in_role, " | ") + " )"
+                );
+
+                builder.add_rule("root", recipient_in_role + " | " + recipient_in_channel);
+            } else {
+                auto not_end = builder.add_rule("not-end",
+                    "[^<] | \"<\" [^|] | \"<|\" [^e] | \"<|e\" [^n] | \"<|en\" [^d] | \"<|end\" [^|] | \"<|end|\" [^>]");
+                auto analysis = builder.add_rule("analysis",
+                    "\"<|channel|>analysis<|message|>\" ( " + not_end + " )* \"<|end|>\"");
+                auto commentary = builder.add_rule("commentary",
+                    "\"<|channel|>commentary<|message|>\" ( " + not_end + " )* \"<|end|>\"");
+
+                auto recipient_in_role = builder.add_rule("recipient_in_role",
+                    "\" to=functions.\" ( " + string_join(tool_rules_recipient_in_role, " | ") + " )"
+                );
+
+                builder.add_rule("root",
+                    "( " + analysis + " \"<|start|>assistant\" )? " +
+                    "( " + commentary + " \"<|start|>assistant\" )? " +
+                    "( " + recipient_in_role + " | " + recipient_in_channel + " )"
+                );
+            }
 
             // Trigger on tool calls that appear in the commentary channel
             data.grammar_triggers.push_back({