Self-Healing CI

We believe these changes will fix the failing build and test:unit tasks. The new getLinkLocationStore helper cast router.stores.location directly to LocationSource, but within router-core's own compilation the RouterWritableStore type has no subscribe member (that member only appears once a framework adapter's module augmentation, e.g. react-router's routerStores.ts, is in scope), so TS2352 correctly flagged the cast as insufficiently overlapping. Routing the cast through unknown first — exactly as the compiler suggested — keeps the intended runtime behavior while satisfying the type checker. Separately, the new test's calls[index]++ tripped noUncheckedIndexedAccess since indexed reads are typed as possibly undefined; a non-null assertion resolves it since index is always within the fixed-size array's bounds.