feat(history): define safe access to Router-managed navigation entries

[LadyBluenotes]

Include:

• Define a non-breaking API for custom RouterHistory implementations.
• Expose only entries Router can reliably know. Do not imply native browser-history enumeration.
• Decide whether persistence is needed. If so, bound storage, validate data, and degrade safely when storage is unavailable.
• Cover memory, browser, hash, reload, back/forward, blocked navigation, and external history mutations with unit and browser E2E tests.
• Measure browser bundle impact.
• Document semantics, limitations, and state-persistence expectations.

Related to closed #3524.