fix(test): move browser.close() after all E2E tests complete

browser.close() on line 274 was firing before tests 14-16 executed,
causing them to crash with 'Target page, context or browser has been
closed'. Moved to after test 16, just before the summary block.

Fixes 3 of 4 E2E failures (remaining 2 are data-dependent map tests).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

test-e2e-playwright.js

@@ -271,8 +271,6 @@ async function run() {
     });
   });
 
-  await browser.close();
-
   // Test 14: Live heatmap opacity stored in localStorage
   await test('Live heatmap opacity persists in localStorage', async () => {
     // Verify localStorage key works (no page load needed — reuse current page)
@@ -315,6 +313,8 @@ async function run() {
     await page.setViewportSize({ width: 1280, height: 720 });
   });
 
+  await browser.close();
+
   // Summary
   const passed = results.filter(r => r.pass).length;
   const failed = results.filter(r => !r.pass).length;