Add conversation pkg

internal/llm/llm.go

@@ -548,6 +548,37 @@ func (m *Message) Validate() error {
 	return nil
 }
 
+// UpdateToolCall replaces the call identified by callId, keeping its
+// position in ToolCalls. The replacement must have the same ID: the
+// corresponding tool response carries it in Message.ToolCallID.
+func (m *Message) UpdateToolCall(call ToolCall) error {
+	if err := call.Validate(); err != nil {
+		return fmt.Errorf("invalid tool call: %w", err)
+	}
+	for i := range m.ToolCalls {
+		if m.ToolCalls[i].ID == call.ID {
+			m.ToolCalls[i] = call
+			return nil
+		}
+	}
+	return fmt.Errorf("not found: call %q", call.ID)
+}
+
+// AddToolCall appends call to the message's ToolCalls. The call must be
+// valid and its ID must not already appear in the message.
+func (m *Message) AddToolCall(call ToolCall) error {
+	if err := call.Validate(); err != nil {
+		return fmt.Errorf("invalid tool call: %w", err)
+	}
+	for _, existing := range m.ToolCalls {
+		if existing.ID == call.ID {
+			return fmt.Errorf("duplicate call id %q", call.ID)
+		}
+	}
+	m.ToolCalls = append(m.ToolCalls, call)
+	return nil
+}
+
 // UnmarshalJSON decodes a message while normalizing a string-valued content
 // field to one text ContentPart. An array-valued content field is decoded in
 // order. If reasoning_content is absent, reasoning is copied into