Restore RNTester tab safe-area behavior

[cortinico]

Summary:

main commit 8d8b8f3b80b6b8ee5eb3d37c3e70feb422858840 changed RNTesterTabsIOSComponentView to force legacy top and bottom insets whenever the native tab bar is at the bottom. The exact-SHA Test All run then failed its iOS RNTester Maestro coverage:

• Cloud run: 19/43 flows failed, mostly because scroll-offset-display was no longer found.
• Focused retries: flatlist-append-maintainvisible failed all 20 attempts across Debug and Release (five attempts in each of two retry rounds) with the same missing element.
• The parent commit 30e2d93b405ef05b8e3daf47455607673ba9d440 completed Test All successfully, so the regression bisects to 8d8b8f3b80b6b8ee5eb3d37c3e70feb422858840.

This keeps the Fabric plugin import needed by the Buck registration fix while restoring the previous, known-green safe-area calculation.

Changelog:

[INTERNAL] [FIXED] - Restore RNTester example bounds when using native iOS tabs.

Test Plan:

• xcrun clang-format --dry-run --Werror packages/rn-tester/RNTesterTabsIOS/ios/RNTesterTabsIOSComponentView.mm — passed with Apple clang-format 21.0.0.
• git diff --check — passed.
• Diffed this branch against 30e2d93b405ef05b8e3daf47455607673ba9d440; the only remaining source change is the plugin import from the original Buck-linking fix.
• Known-green parent run: https://github.com/react/react-native/actions/runs/37553922113
• Regressed exact-SHA run: https://github.com/react/react-native/actions/runs/37564021203

A full iOS Maestro run was not reproduced locally because it requires the RNTester simulator/cloud setup used by GitHub Actions. PR CI is expected to provide the end-to-end confirmation.

Risk / limitations:

Low: this restores the exact safe-area behavior from the green parent while retaining the registration import. The internal Buck-built RNTester may return to its pre-8d8b8f3b content bounds; the component-linking fix itself remains intact.