Add Border visual regression tests (#59343)

Summary:
Pull Request resolved: #59343

Add a Maestro visual suite for `Border` using existing RNTester examples. Capture stable cropped checkpoints after opening each example and settling animations.

See `packages/rn-tester/visual-tests/suites/border.md` for the example and checkpoint inventory.

Changelog: [Internal]

Reviewed By: Abbondanzo

Differential Revision: D126723202

Author: cortinico

packages/rn-tester/visual-tests/flows/border.yml

@@ -0,0 +1,44 @@
+appId: ${APP_ID}
+---
+- runFlow:
+    file: ../helpers/open-example.yml
+    env:
+      EXAMPLE_URL: rntester://example/BorderExample/corner-radii
+- extendedWaitUntil:
+    visible:
+      id: 'border-test-corner-radii'
+    timeout: 15000
+- waitForAnimationToEnd:
+    timeout: 5000
+- takeScreenshot:
+    path: ${VISUAL_OUTPUT_DIR}/border/corner-radii/default
+    cropOn:
+      id: 'border-test-corner-radii'
+- runFlow:
+    file: ../helpers/open-example.yml
+    env:
+      EXAMPLE_URL: rntester://example/BorderExample/child-clipping-radius
+- extendedWaitUntil:
+    visible:
+      id: 'border-test-child-clipping-radius'
+    timeout: 15000
+- waitForAnimationToEnd:
+    timeout: 5000
+- takeScreenshot:
+    path: ${VISUAL_OUTPUT_DIR}/border/child-clipping-radius/default
+    cropOn:
+      id: 'border-test-child-clipping-radius'
+- runFlow:
+    file: ../helpers/open-example.yml
+    env:
+      EXAMPLE_URL: rntester://example/BorderExample/equal-width-borders
+- extendedWaitUntil:
+    visible:
+      id: 'border-test-equal-width-borders'
+    timeout: 15000
+- waitForAnimationToEnd:
+    timeout: 5000
+- takeScreenshot:
+    path: ${VISUAL_OUTPUT_DIR}/border/equal-width-borders/default
+    cropOn:
+      id: 'border-test-equal-width-borders'

packages/rn-tester/visual-tests/suites/border.md

@@ -0,0 +1,9 @@
+# Border visual tests
+
+| Example | Checkpoints |
+| --- | --- |
+| `corner-radii` | Initial rendering |
+| `child-clipping-radius` | Initial rendering |
+| `equal-width-borders` | Initial rendering |
+
+Screenshots use the existing RNTester example crops. Each example starts from a fresh app launch; captures wait for the target and for animations to settle.