feat(captain): align task payload persistence

internal/model/copilot_models.go

@@ -2,6 +2,9 @@ package model
 
 import (
 	"encoding/json"
+	"fmt"
+
+	"gorm.io/gorm"
 )
 
 // --- Copilot Thread Model ---
@@ -62,6 +65,30 @@ type CopilotMessage struct {
 
 func (CopilotMessage) TableName() string { return "copilot_messages" }
 
+// BeforeSave mirrors Chatwoot's CopilotMessage JSON key validation so
+// reloadable tool-call state stays compatible with the reused frontend.
+func (m *CopilotMessage) BeforeSave(tx *gorm.DB) error {
+	if len(m.Message) == 0 {
+		return nil
+	}
+	var msgMap map[string]interface{}
+	if err := json.Unmarshal(m.Message, &msgMap); err != nil {
+		return err
+	}
+	allowed := map[string]bool{
+		"content":          true,
+		"reasoning":        true,
+		"function_name":    true,
+		"reply_suggestion": true,
+	}
+	for key := range msgMap {
+		if !allowed[key] {
+			return fmt.Errorf("message contains invalid attribute: %s", key)
+		}
+	}
+	return nil
+}
+
 // GetMessageContent extracts the "content" field from the JSONB message.
 func (m *CopilotMessage) GetMessageContent() string {
 	var msgMap map[string]interface{}