Skip fields starting with `_` in pretty-printed struct output
to avoid cluttering displays with internal/private state (and/or accessing
private properties which have errors Bp).
Deats,
- add `if k[0] == '_': continue` check to skip private fields
- change nested `if isinstance(v, Struct)` to `elif` since we
now have early-continue for private fields
- mv `else:` comment to clarify it handles top-level fields
- fix indentation of `yield` statement to only output
non-private, non-nested fields
(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code