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 {