fix(web): exclude the exact five-minute boundary from the lease warning

Address review feedback on the question lease UI:

- The warning is for less than five minutes remaining, so a lease with
  exactly five minutes left no longer shows it.
- Add a boundary test covering both five minutes and four minutes
  fifty-nine seconds.
- Correct the i18n section of apps/pythinker-web/AGENTS.md: the app ships
  a single English locale, so the bilingual parity rule described a
  directory that does not exist.

Author: elkaix

apps/pythinker-web/AGENTS.md

@@ -23,13 +23,13 @@ The browser web UI for Pythinker Code — a peer to the TUI in `apps/pythinker-c
 - Shared components go in `src/components/`; reusable logic goes in `src/composables/` with a `use` prefix.
 - There is **no auto-import plugin** and **no path alias** — `#/` and `@/` are intentionally unused. Write relative imports (`../i18n`, `./config`).
 
-## i18n (normative — keeping locales in sync is manual)
+## i18n (normative — the app is English-only)
 
 - Setup: `src/i18n/index.ts`, vue-i18n in Composition mode (`legacy: false`), fallback `en`. The active locale is persisted in `localStorage` under `pythinker-locale`.
-- Locale files: `src/i18n/locales/{en,zh}/<namespace>.ts`, each `export default { ... } as const`. New namespaces are registered in `src/i18n/locales/index.ts`.
+- **`en` is the only locale.** `src/i18n/locales/` contains exactly one directory, and `locales/index.ts` registers only `en`. Do not add a second locale, and do not "restore parity" with one that does not exist.
+- Locale files: `src/i18n/locales/en/<namespace>.ts`, each `export default { ... } as const`. New namespaces are registered in `src/i18n/locales/index.ts`.
 - Reference with `const { t } = useI18n()` and `t('namespace.key')` (same form in templates).
-- **Adding a key:** add it to **both** `en/<ns>.ts` and `zh/<ns>.ts`. **Adding a namespace:** create the file in both locales **and** register it in `locales/index.ts`.
-- There is **no automated missing-key or en/zh parity check**. Keeping the two locales in sync is a manual responsibility — do not leave a key present in only one locale.
+- **Adding a key:** add it to `en/<ns>.ts`. **Adding a namespace:** create the file under `en/` **and** register it in `locales/index.ts`.
 
 ## Commands
 

apps/pythinker-web/src/components/QuestionCard.vue

@@ -40,7 +40,7 @@ const leaseWarning = computed(() => {
   const expiresAt = Date.parse(props.question.expiresAt);
   if (Number.isNaN(expiresAt)) return undefined;
   const remainingMs = expiresAt - now.value;
-  if (remainingMs <= 0 || remainingMs > 5 * 60_000) return undefined;
+  if (remainingMs <= 0 || remainingMs >= 5 * 60_000) return undefined;
   if (remainingMs < 60_000) return t('question.expiresSoonSeconds');
   const minutes = remainingMinutes.value;
   if (minutes === undefined) return undefined;

apps/pythinker-web/test/question-card-lifecycle.test.ts

@@ -1,6 +1,6 @@
 import { mount } from '@vue/test-utils';
 import { createI18n } from 'vue-i18n';
-import { afterEach, describe, expect, it } from 'vitest';
+import { afterEach, describe, expect, it, vi } from 'vitest';
 
 import QuestionCard from '../src/components/QuestionCard.vue';
 import type { UIQuestion } from '../src/types';
@@ -88,4 +88,28 @@ describe('QuestionCard lifecycle', () => {
     expect(soon.find('.qexpires').text()).toBe('Expires in 2 min');
     expect(later.find('.qexpires').exists()).toBe(false);
   });
+
+  it('hides the expiry warning at five minutes and shows it at four minutes fifty-nine seconds', () => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date('2026-01-01T00:00:00.000Z'));
+    try {
+      const boundary = mountCard(question(new Date(Date.now() + 5 * 60_000).toISOString()));
+      const soon = mountCard(question(new Date(Date.now() + 4 * 60_000 + 59_000).toISOString()));
+
+      expect(boundary.find('.qexpires').exists()).toBe(false);
+      expect(soon.find('.qexpires').exists()).toBe(true);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
+  it('ignores Enter while minimized', async () => {
+    const wrapper = mountCard(question(new Date(Date.now() + 20 * 60_000).toISOString()));
+
+    document.dispatchEvent(new KeyboardEvent('keydown', { key: '1', bubbles: true }));
+    await wrapper.find('.qmin').trigger('click');
+    document.dispatchEvent(new KeyboardEvent('keydown', { key: 'Enter', bubbles: true }));
+
+    expect(wrapper.emitted('answer')).toBeUndefined();
+  });
 });