[tests] update selection overlay tests after canvas migration (#5173)

* [fix] update selection overlay tests after canvas migration

Update browser tests to work with canvas-based selection overlay introduced in PR #5158.
Replaces DOM-based .selection-overlay-container checks with .selection-toolbox visibility
and converts border visibility tests to canvas screenshot comparisons.

Fixes #5158

* [chore] remove unused file flagged by knip

* [fix] adjust test expectations for canvas-based positioning

- Skip animated webp test unrelated to selection overlay changes
- Update toolbox position expectations to match canvas-based coordinates
- Canvas positioning uses different coordinate system than DOM overlay

* [fix] improve positioning test flexibility and revert webp skip

- Make toolbox position test more flexible for canvas-based coordinates
- Revert animated webp test skip as requested in review
- Canvas positioning varies more than DOM, use reasonable bounds instead

* Update test expectations [skip ci]

* [refactor] address review comments - use fixture locators

- Add selectionToolbox locator to ComfyPage fixture as requested
- Replace .isVisible() === false with .not.toBeVisible() pattern
- Update all selection toolbox locators to use fixture instead of inline selectors
- Improves maintainability and follows established patterns

* [refactor] use fixture canvas locator for screenshots

Replace inline canvas locators with comfyPage.canvas fixture property
for consistency and maintainability as suggested in review.

---------

Co-authored-by: github-actions <github-actions@github.com>

browser_tests/tests/nodeHelp.spec.ts

@@ -41,15 +41,12 @@ test.describe('Node Help', () => {
       // Select the node with panning to ensure toolbox is visible
       await selectNodeWithPan(comfyPage, ksamplerNodes[0])
 
-      // Wait for selection overlay container and toolbox to appear
-      await expect(
-        comfyPage.page.locator('.selection-overlay-container')
-      ).toBeVisible()
-      await expect(comfyPage.page.locator('.selection-toolbox')).toBeVisible()
+      // Wait for selection toolbox to appear
+      await expect(comfyPage.selectionToolbox).toBeVisible()
 
       // Click the help button in the selection toolbox
-      const helpButton = comfyPage.page.locator(
-        '.selection-toolbox button:has(.pi-question-circle)'
+      const helpButton = comfyPage.selectionToolbox.locator(
+        'button:has(.pi-question-circle)'
       )
       await expect(helpButton).toBeVisible()
       await helpButton.click()