fix(react-router): show pages swapped into one view

[djoume]

Issue number: resolves #31525

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What is the current behavior?

When an outlet's only route is a splat whose element renders <Routes>, every navigation swaps a new IonPage into the same view item. Each new page mounts with ion-page-invisible. isDuplicateTransition compares only the entering and leaving view ids, so the swap looks like a repeat of the previous transition and is skipped. The page stays at opacity: 0, which leaves a blank screen. This happens:

• from the second root navigation on, with path="/*";
• from the second navigation of any kind, with a bare path="*".

What is the new behavior?

• lastTransition also records the entering IonPage element, and a transition only counts as a duplicate when that element is the same too. A newly mounted page now takes the normal transitionPage path, so it is revealed and fires its lifecycle events. A second call for the same navigation, with the same element, is still skipped.
• Adds a root-single-view test app, served under its own basename like root-splat-sibling, and root-single-view.spec.ts:
  • with /*: three root navigations each leave the target page visible;
  • with a bare * (?splat=bare): three pushes each leave the target page visible.

Does this introduce a breaking change?

• Yes
• No

Other information

• The new spec fails at the second navigation without the StackManager change, and passes with it.
• With the change, reactrouter6-react18 passes the full Playwright suite (127/127) and the full Cypress suite (206/206). npm run typecheck and npm run lint are clean.
• An earlier version revealed the page with an early return for same-view swaps. It broke tab-lifecycle.spec.ts (FW-6788), because returning tabs need transitionPage to fire ionViewDidEnter. Fixing the duplicate check keeps that path.

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