Support running on Bun

### Feature Summary

There are potential performance benefits to being able to run Harper on Bun. And we generally want Harper to have as much interoperability with different runtimes as possible.

### Problem This Solves

Performance and broader interoperability.

### Proposed Solution

Test Bun and determine what needs to be fixed.

### User Stories

_No response_

### Alternatives Considered

_No response_

### Priority/Impact

Medium - important but not urgent

### 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