chore: enable clippy::redundant_clone (#3489)

Created this PR by:

- adding `redundant_clone` to `[workspace.lints.clippy]` in
`cargo-rs/Cargol.toml`
- running `cargo clippy --tests --fix`
- running `just fmt`

Though I had to clean up one instance of the following that resulted:

```rust
let codex = codex;
```

codex-rs/mcp-server/src/outgoing_message.rs

@@ -299,7 +299,7 @@ mod tests {
         let Ok(expected_params) = serde_json::to_value(&event) else {
             panic!("Event must serialize");
         };
-        assert_eq!(params, Some(expected_params.clone()));
+        assert_eq!(params, Some(expected_params));
     }
 
     #[tokio::test]