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/codex_tool_runner.rs

@@ -222,7 +222,7 @@ async fn run_codex_tool_session_inner(
                     }
                     EventMsg::TaskComplete(TaskCompleteEvent { last_agent_message }) => {
                         let text = match last_agent_message {
-                            Some(msg) => msg.clone(),
+                            Some(msg) => msg,
                             None => "".to_string(),
                         };
                         let result = CallToolResult {

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();

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]