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/tui/src/chatwidget/tests.rs

@@ -352,7 +352,7 @@ fn exec_approval_decision_truncates_multiline_and_long_commands() {
     let long = format!("echo {}", "a".repeat(200));
     let ev_long = ExecApprovalRequestEvent {
         call_id: "call-long".into(),
-        command: vec!["bash".into(), "-lc".into(), long.clone()],
+        command: vec!["bash".into(), "-lc".into(), long],
         cwd: std::env::current_dir().unwrap_or_else(|_| PathBuf::from(".")),
         reason: None,
     };