fix: align Plus no-payment flow and step5 completion

tests/background-step5-post-completion-validation.test.js

@@ -110,6 +110,7 @@ async function waitForTabStableComplete() {}
 ${extractFunction('parseUrlSafely')}
 ${extractFunction('isSignupEntryHost')}
 ${extractFunction('isLikelyLoggedInChatgptHomeUrl')}
+${extractFunction('isStep5CompletionChatgptUrl')}
 ${extractFunction('getStep5SubmitStateFromContent')}
 ${extractFunction('recoverStep5SubmitRetryPageOnTab')}
 ${extractFunction('validateStep5PostCompletion')}
@@ -138,3 +139,65 @@ return {
     true
   );
 });
+
+test('step 5 post-completion validation rejects non-chatgpt success candidates', async () => {
+  const api = new Function(`
+const logs = [];
+const chrome = {
+  tabs: {
+    async get() {
+      return { url: 'https://auth.openai.com/sign-in-with-chatgpt/codex/consent' };
+    },
+  },
+};
+
+async function sendToContentScriptResilient(source, message) {
+  if (message.type === 'GET_STEP5_SUBMIT_STATE') {
+    return {
+      retryPage: false,
+      retryEnabled: false,
+      maxCheckAttemptsBlocked: false,
+      userAlreadyExistsBlocked: false,
+      successState: 'oauth_consent',
+      profileVisible: false,
+      errorText: '',
+      unknownAuthPage: false,
+      url: 'https://auth.openai.com/sign-in-with-chatgpt/codex/consent',
+    };
+  }
+  throw new Error('unexpected message type: ' + message.type);
+}
+
+async function addLog(message, level, meta) {
+  logs.push({ message, level, meta });
+}
+
+async function waitForTabStableComplete() {}
+
+${extractFunction('parseUrlSafely')}
+${extractFunction('isSignupEntryHost')}
+${extractFunction('isLikelyLoggedInChatgptHomeUrl')}
+${extractFunction('isStep5CompletionChatgptUrl')}
+${extractFunction('getStep5SubmitStateFromContent')}
+${extractFunction('recoverStep5SubmitRetryPageOnTab')}
+${extractFunction('validateStep5PostCompletion')}
+
+return {
+  run() {
+    return validateStep5PostCompletion(99, {});
+  },
+  snapshot() {
+    return { logs };
+  },
+};
+`)();
+
+  await assert.rejects(
+    api.run(),
+    /尚未跳转到 https:\/\/chatgpt\.com/
+  );
+  assert.equal(
+    api.snapshot().logs.some(({ message }) => /非 chatgpt\.com 的步骤 5 完成候选/.test(message)),
+    true
+  );
+});