feat(cli): add --json to org members

[MayurK-cmd]

Closes #529

[Maxerns]

Thanks this matches #529 well.

The JSON output has exactly the fields the issue asks for: user_id, role, and has_keys, with the actual key material never serialized. Empty membership correctly returns [], the default human-readable output is unchanged, and the escaping case is covered too.

I also forced has_keys to always return true as a mutation check, and exactly the serializer test failed, so the coverage is protecting the real mapping rather than just the output shape.

I ran the focused tests, the full binary suite, fmt, and clippy locally, all green.

[Maxerns]

Resolved the merge conflict with main it was just the two test-import lines colliding with #589's additions, so I merged main in and kept both import sets. Full bin suite (36 tests), clippy and fmt all pass on the merged tree. Over to CI now.