fix(mcp): harden dashboard dispatch lifecycle

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

cmd/dashboard/controller/mcp_result_encoding.go

@@ -0,0 +1,14 @@
+package controller
+
+import "encoding/json"
+
+func marshalMCPToolResult(result any) (string, error) {
+	if result == nil {
+		return "{}", nil
+	}
+	b, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}