refactor(scenario): remove validateCode — assertions live in execCode

- drop validateCode column, DTOs, service mappings, and scheduler branch
- remove parseValidateResult helper and ValidateResult interface
- inject playwright expect into code executor for direct use in execCode
- strip validateCode from MCP tool schemas, client types, and UI forms

client/src/api/client.ts

@@ -274,14 +274,12 @@ export const scenarioCredentials = {
 export interface CreateStepPayload {
   title?: string;
   execCode?: string;
-  validateCode?: string;
 }
 
 export interface UpdateStepPayload {
   title?: string;
   order?: number;
   execCode?: string;
-  validateCode?: string;
 }
 
 export const steps = {

client/src/api/types.ts

@@ -66,7 +66,6 @@ export interface ScenarioStep {
   order: number;
   title: string | null;
   execCode: string | null;
-  validateCode: string | null;
   createdAt: string;
   updatedAt: string;
 }

client/src/i18n/locales/en.json

@@ -183,9 +183,7 @@
     "form_session_placeholder": "e.g. my-session",
     "form_session_required": "Session name is required",
     "form_exec_code": "Exec code",
-    "form_exec_code_placeholder": "return await page.title();",
-    "form_validate_code": "Validate code",
-    "form_validate_code_placeholder": "return { success: result !== null, description: \"…\" };"
+    "form_exec_code_placeholder": "return await page.title();"
   },
   "runs": {
     "title": "Runs",

client/src/pages/scenario/CreateStepPage.tsx

@@ -16,7 +16,6 @@ export function CreateStepPage() {
   const [scenario, setScenario] = useState<Scenario | null>(null);
   const [title, setTitle] = useState('');
   const [execCode, setExecCode] = useState('');
-  const [validateCode, setValidateCode] = useState('');
   const [saving, setSaving] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
@@ -36,7 +35,6 @@ export function CreateStepPage() {
       await steps.create(id!, {
         title: title.trim() || undefined,
         execCode: execCode.trim() || undefined,
-        validateCode: validateCode.trim() || undefined,
       });
       toast.success('Step created');
       navigate(`/scenarios/${id}`);
@@ -77,10 +75,6 @@ export function CreateStepPage() {
               <label className={styles.fieldLabel}>{t('steps.form_exec_code')}</label>
               <CodeEditor value={execCode} onChange={setExecCode} rows={6} />
             </div>
-            <div className={styles.formField}>
-              <label className={styles.fieldLabel}>{t('steps.form_validate_code')}</label>
-              <CodeEditor value={validateCode} onChange={setValidateCode} rows={6} />
-            </div>
           </div>
 
           <div className={styles.formActions}>

client/src/pages/scenario/EditStepPage.tsx

@@ -17,7 +17,6 @@ export function EditStepPage() {
   const [step, setStep] = useState<ScenarioStep | null>(null);
   const [title, setTitle] = useState('');
   const [execCode, setExecCode] = useState('');
-  const [validateCode, setValidateCode] = useState('');
   const [loading, setLoading] = useState(true);
   const [saving, setSaving] = useState(false);
   const [error, setError] = useState<string | null>(null);
@@ -30,7 +29,6 @@ export function EditStepPage() {
         setStep(st);
         setTitle(st.title ?? '');
         setExecCode(st.execCode ?? '');
-        setValidateCode(st.validateCode ?? '');
       })
       .catch((err: Error) => setError(err.message))
       .finally(() => setLoading(false));
@@ -44,7 +42,6 @@ export function EditStepPage() {
       await steps.update(id!, stepId!, {
         title: title.trim() || undefined,
         execCode: execCode.trim() || undefined,
-        validateCode: validateCode.trim() || undefined,
       });
       toast.success('Step updated');
       navigate(`/scenarios/${id}`);
@@ -88,10 +85,6 @@ export function EditStepPage() {
                 <label className={styles.fieldLabel}>{t('steps.form_exec_code')}</label>
                 <CodeEditor value={execCode} onChange={setExecCode} rows={6} />
               </div>
-              <div className={styles.formField}>
-                <label className={styles.fieldLabel}>{t('steps.form_validate_code')}</label>
-                <CodeEditor value={validateCode} onChange={setValidateCode} rows={6} />
-              </div>
             </div>
 
             <div className={styles.formActions}>