fix(browser_tests): use getByRole for interactive elements

Replace fragile CSS selectors with Playwright getByRole() for better

accessibility-based testing:

- bottomPanelShortcuts.spec.ts: button[aria-label] -> getByRole

- execution.spec.ts: .p-dialog-close-button -> getByRole

- backgroundImageUpload.spec.ts: button:has(.pi-*) -> getByRole

- nodeHelp.spec.ts: button:has(.pi-question) -> getByRole

- BaseDialog.ts: closeButton uses getByRole

- ComfyNodeSearchBox.ts: Add button uses getByRole

- Topbar.ts: close-button uses getByRole

Amp-Thread-ID: https://ampcode.com/threads/T-019c155c-92e1-76f3-b6ce-7fc3ffa11582
Co-authored-by: Amp <amp@ampcode.com>

browser_tests/tests/nodeHelp.spec.ts

@@ -88,7 +88,9 @@ test.describe('Node Help', { tag: ['@slow', '@ui'] }, () => {
       await ksamplerNode.hover()
 
       // Click the help button
-      const helpButton = ksamplerNode.locator('button:has(.pi-question)')
+      const helpButton = ksamplerNode.getByRole('button', {
+        name: /learn more/i
+      })
       await expect(helpButton).toBeVisible()
       await helpButton.click()
 
@@ -118,7 +120,9 @@ test.describe('Node Help', { tag: ['@slow', '@ui'] }, () => {
         .filter({ hasText: 'KSampler' })
         .first()
       await ksamplerNode.hover()
-      const helpButton = ksamplerNode.locator('button:has(.pi-question)')
+      const helpButton = ksamplerNode.getByRole('button', {
+        name: /learn more/i
+      })
       await helpButton.click()
 
       // Verify help page is shown