Give listFeeds its container: Add a feed loads its Popular list again

The dialog and the Directory/Popular pane both rendered into id="popular", and
listFeeds looked it up by id, so the dialog's list landed in the pane behind it.

Fixes #1

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SZbKERNSt4vQfyGV8rvkqp

tests/ui/app.spec.js

@@ -703,6 +703,12 @@ test('Popular lists what everyone here reads, but never a private feed', async (
   await expect(offered.filter({ hasText: /Test Subscriptions/ })).toHaveCount(0);
   await expect(offered.filter({ hasText: /Paid Show|paid-show/ })).toHaveCount(0);
 
+  // Add a feed opened over Directory fills its own list, not the pane behind it.
+  await piper.locator('#addFeed').click();
+  await expect(piper.locator('#modalCard .childrow', { hasText: 'Test Show' })).toBeVisible();
+  await expect(offered).toHaveCount(dir.length);
+  await piper.locator('#modalCard button[title="Cancel"]').click();
+
   const row = async () =>
     (await (await piper.request.get('/api/popular')).json()).find(p => p.id === 'test-show');
   const before = await row();