- no need for a separate effect since we can use the existing one
- no need to cancel the similar artists query upon entering, since the
unregister callback already does it
- expose a shell-bridge cancel primitive for similar-artists loading
- stop stale similar-artists streams from the artist-detail route lifecycle
- keep the legacy loader abort-only and make abort logs page-agnostic
- update bridge and route tests for the new cleanup path
- add a canonical TanStack route for artist-detail and keep the legacy page as the renderer target
- expose page-level artist-detail navigation on the shell bridge for legacy callers
- remove artist-detail-specific routing, origin stack, and back-label logic from the shared shell helpers
- add canonical /artist-detail/:source/:id TanStack route
- hand the legacy page off through the shell bridge
- remove artist-detail branching from generic shell helpers
