feat: ✨ add role capabilities to cluster node

[Tochemey]

Add role-based capabilities to your cluster nodes so SpawnOn can place Actors exactly where they’ll run best. By tagging nodes with meaningful roles—like compute, io, gpu, or edge—you give the runtime a simple, explicit signal for locality and resource fit. That keeps placement decisions fast and predictable, and it avoids the guesswork that creeps in when every node looks identical on paper but behaves differently under load.

Roles cleanly separate concerns: they describe what a node is for, so your Actors can be deployed to where they should live. Instead of scattering lightweight services across heavyweight machines—or vice versa—you steer background workers, latency-sensitive Actors, and bursty jobs to the right hardware tiers. In practice, that means fewer noisy-neighbor issues, better cache hit rates, and less cross-node chatter, because SpawnOn can honor both intention and topology.

It’s a best practice to specify roles from day one. You don’t want a low-power application consuming capacity earmarked for a mission-critical, resource-intensive workload. Even if today’s cluster has a single node type, add a default role now: it costs nothing at runtime, and it future-proofs your deployment model. As you expand, roles let you scale smoothly, run safer canaries, control blast radius, and keep costs in check—all without refactoring placement code or retraining your team.