Avoid ANSI codes in debug! messages (#15843)

## Summary

I spent time trying to figure out how to support this but came up empty.
It _seems_ like maybe the `DefaultFields` implementation in
`tracing-subscriber` uses debug formatting for fields...? So if you have
a string with ANSI codes, they end up printing as unformatted values? I
even reverted all our custom formatting in `logging.rs` and saw the same
thing.

Closes https://github.com/astral-sh/uv/issues/15840.

crates/uv-auth/src/middleware.rs

@@ -2235,7 +2235,7 @@ mod tests {
         assert!(matches!(
             client.get(server.uri()).send().await,
             Err(reqwest_middleware::Error::Middleware(_))
-        ),);
+        ));
 
         Ok(())
     }