fix(react-router): reveal pages in one view

[Elements2720]

Summary

Issue #31525 occurs when a single Ionic view swaps different IonPage elements while retaining the same view ID:

StackManager duplicate guard
  view IDs only
    new IonPage is treated as the previous transition
    page remains ion-page-invisible
  view IDs + entering IonPage element
    new page follows the normal transition path
    page is revealed

This PR:

• Includes the entering page element in duplicate-transition detection.
• Adds a root-single-view reproduction app.
• Covers successive root navigations with /* and pushes with bare *.

Resolves #31525

Evidence

• Before: the focused regression suite failed both scenarios with ion-page-invisible remaining on the entering page.
• After: npx playwright test root-single-view root-splat-sibling --retries=0 passed all 7 tests.
• Additional checks: React Router typecheck, ESLint, Prettier, package build, and test-app build passed.

Merge Danger

Door: Two-way

The change is limited to React Router transition deduplication and its regression test app. It preserves duplicate suppression when the same page element is involved.

Blast Radius: react-router

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