Add a CLI or configuration option to send logs to stderr

### Feature Summary

For many CLI operations, it can be very convenient to rely on stdout to only have the intended CLI output (for piping purposes), and not have log messages mixed in (which can occur with config like `level: trace` and `stdStreams: true`). We would like to be able to configure and/or set the behavior so you can tell the logger to send logs only to stderr.

### Problem This Solves

This makes it easier to use the CLI with piping/scripting.

### Proposed Solution

A CLI argument of `--log-to-stderr` could work. Or a configuration option like `stdStreams: 'stderr'`. Or an env variable like `HARPER_LOG_TO_STDERR`. 🤷

### User Stories

_No response_

### Alternatives Considered

_No response_

### Priority/Impact

None

### Examples or References

_No response_

### Additional Context

_No response_

### Are you planning to fix this issue?

No, just reporting the issue

### First-time contributor support

- [ ] I'm new to contributing and would appreciate guidance on the process
- [ ] I'd like help understanding the project structure
- [ ] I need assistance with setting up the development environment
- [ ] I'm comfortable contributing, but new to this project specifically