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/message_processor.rs

@@ -531,7 +531,6 @@ impl MessageProcessor {
 
         // Spawn the long-running reply handler.
         tokio::spawn({
-            let codex = codex.clone();
             let outgoing = outgoing.clone();
             let prompt = prompt.clone();
             let running_requests_id_to_codex_uuid = running_requests_id_to_codex_uuid.clone();