fix: add Scope.Scope support to AtomRuntime.subscriptionRef and subscribable

[mikearnaldi]

Summary

• Add Scope.Scope to the effect requirements type signature for AtomRuntime.subscriptionRef and AtomRuntime.subscribable, aligning them with AtomRuntime.atom and AtomRuntime.fn which already support scoped effects
• Add test case SubscriptionRef/runtime/scoped to verify finalizers work correctly when using scoped effects with subscriptionRef

This allows using Effect.addFinalizer and Effect.forkScoped directly in subscriptionRef without needing to provide Layer.scope as a workaround.