chore: alias set() onto KaiselNavigator for symmetry with KaiselRouter

[Mastersam07]

KaiselRouter.set(...) and KaiselNavigator.restoreStack(...) do the same thing under different names.

From context.shell().current you only get a KaiselNavigator, so code that deliberately assigns a branchs stack reads as state restoration:

// "pop this tab back to its root" when the active tab is tapped again
shell.current.restoreStack([DashboardTabRoute(item)]);

versus the equivalent at the root:

router.set([SomeRoute()]);

restoreStack is the right name for its other caller (state restoration), but at a deliberate-assignment call site it misleads — a reviewer reasonably asks what is being restored.

Suggestion

Add set to KaiselNavigator as an alias for restoreStack, or rename for symmetry and keep the old name deprecated for a release. Small, but it is on the path anyone building a branched shell with "tap active tab to reset" behaviour will walk.