worker: prefix run id to all logs for that run

When a run logs to GCP, it can be hard to know which run it logs to. You get output like this:

[R/T] ❯ Starting operation 1

Which isn't helpful.

What I'd really like is to automatically prefix the run to the log line somehow, so I can differentiate.

The dumb obvious way is:

[R/T] ❯ [ef8acfe6-943d-4b2f-9bff-739e70e6b9eb] Starting operation 1

A smarter way to do this might be by adding some kind of metadata label for GCP, a la #1043. That would be visually tidier I think?

Either way I think we need support for this in the Logger itself, some kind of prefix. Not the namespace, but something to go along side it. Then each Run needs its own private logger instance.

Note that these are system logs produced by the runtime and engine itself - not logs within the sandbox. Those are private.

Start by locating the worker's Run and Logger entry points and tracing how system logs are emitted to GCP. Compare a logger prefix with GCP metadata labels, then define the chosen run-identification behavior and verify that logs from separate runs remain distinguishable without changing sandbox logs.