`windows-registry` should allow OsStr paths

### Summary

Windows Registry paths are not generally guaranteed to be UTF-8. The paths are often used as inputs and outputs to other APIs, which take and return OS strings (OsStr or HSTRING, etc, which don't enforce encoding) requiring a _lossy or unwrap_or_default etc at the API boundary.

### Crate manifest

```TOML

```

### Crate code

```Rust

```

Start by locating the windows-registry crate APIs that accept or return registry paths and inspect how they currently represent strings. Done means registry paths can be handled as OsStr-compatible values without requiring lossy conversion, unwrap_or_default, or UTF-8 assumptions at API boundaries.

Written by the indexing model from the issue text.