test(post-form): assert datetime-local picker, prefill, and required-date gate

Covers the theme datetime override: the date field renders as
<input type="datetime-local">, is prefilled with the current local time in
the native value format, and clearing it blocks submit client-side (no
success notice) — the guard that keeps an invalid date from wiping the
FilePond photo list on a server re-render.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/ui/post/post-form-ux.spec.js

@@ -116,6 +116,29 @@ test('uploaded photos are renamed photo-1..N and the order field never hits fron
     expect(md).not.toContain('photo_order');
 });
 
+// ── Date field is a native datetime-local picker, prefilled, and required ─────
+test('date field renders as a datetime-local picker, prefilled with now and required', async ({ page }) => {
+    await page.goto('/post');
+    const date = page.locator('input[name="data[date]"]');
+
+    // Grav's deprecated datetime field used to fall back to a plain text box;
+    // the theme override renders a real picker instead.
+    await expect(date).toHaveAttribute('type', 'datetime-local');
+    // post-form.js prefills the current local time in the value format the
+    // native input expects (YYYY-MM-DDTHH:MM).
+    await expect(date).toHaveValue(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}$/);
+
+    // Clearing it and submitting must be blocked client-side (this is what keeps
+    // an invalid/empty date from round-tripping to the server and wiping the
+    // FilePond photo list on a re-render).
+    await date.fill('');
+    await page.fill('input[name="data[title]"]', `UI date-${Date.now()}`);
+    await fillEditor(page, 'datetime picker validation test');
+    await page.locator('.btn-post').evaluate(el => el.click());
+    await expect(date).toHaveClass(/field-invalid/);
+    await expect(page.locator('.notices.success, .notices.green')).toHaveCount(0);
+});
+
 // ── R18: Get Weather is gated on coordinates ──────────────────────────────────
 test('R18: Get Weather is disabled until Get Location provides coordinates', async ({ page, context }) => {
     await context.grantPermissions(['geolocation']);