Python SDK harness logs from child processes missing correct portability_worker_id in Dataflow

### What would you like to happen?

Hey team we’re hitting a logging gap with native code (pybind / C++) in the Python SDK harness. It seems like `boot.go` launches a bunch of Python child processes, and then pipes its outputs stdout/stderr to `BufferedLogger` -> `FnLogging`. But because it never goes through the Python Fn logging stack, so we lose the same worker attribution you get from normal SDK logs - particularly `portability_worker_id`.

Concretely, our Python logs come with the metadata `jsonPayload.portability_worker_id=sdk-0-0_sibling_5`. But our pybind'd C++ code logs has `jsonPayload.portability_worker_id=sdk-0-0` (from `boot.go`), so we can't correlate it.

I wonder if easily fixable in `boot.go`? In https://github.com/apache/beam/blob/ae536b6f0f83b978854f1d6852fbacb62a3e5ec0/sdks/python/container/boot.go#L321, instead of:

```go
bufLogger := tools.NewBufferedLogger(logger)
```

We would do something like:

```go
workerCtx := grpcx.WriteWorkerID(context.Background(), workerId)
bufLogger := tools.NewBufferedLoggerWithFlushInterval(workerCtx, logger, 100*time.Millisecond)
```

I have no idea if on the Dataflow Unified Harness, will actually pick up the `workerId` on the Google logging sink, which is why I'm asking.

## EDIT 2026-04-17
I got this working by creating a separate logger per worker:

```go
workerCtx := grpcx.WriteWorkerID(context.Background(), workerId)
// Separate Fn logging client per worker so the first Log on this Logger
// opens the stream with the correct worker_id metadata (shared Logger
// would reuse the first stream only).
workerLogger := &tools.Logger{Endpoint: *loggingEndpoint}
bufLogger := tools.NewBufferedLoggerWithFlushInterval(workerCtx, workerLogger, 100*time.Millisecond)
...
workerLogger.Printf(workerCtx, "Executing Python (worker %v): python %v", workerId, strings.Join(args, " "))
cmd := StartCommandEnv(map[string]string{"WORKER_ID": workerId}, os.Stdin, bufLogger, bufLogger, "python", args...)
```

### Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

### Issue Components

- [x] Component: Python SDK
- [ ] Component: Java SDK
- [ ] Component: Go SDK
- [ ] Component: Typescript SDK
- [ ] Component: IO connector
- [ ] Component: Beam YAML
- [ ] Component: Beam examples
- [ ] Component: Beam playground
- [ ] Component: Beam katas
- [ ] Component: Website
- [ ] Component: Infrastructure
- [ ] Component: Spark Runner
- [ ] Component: Flink Runner
- [ ] Component: Samza Runner
- [ ] Component: Twister2 Runner
- [ ] Component: Hazelcast Jet Runner
- [x] Component: Google Cloud Dataflow Runner