Claude review: samples: rust: add Rust serial device bus sample device driver

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

The sample is clean and demonstrates the abstraction well.

```rust
+    fn receive<'bound>(
+        sdev: &'bound serdev::Device<Bound>,
+        _this: Pin<&Self>,
+        data: &[u8],
+    ) -> usize {
+        let _ = sdev.write_all(data, serdev::Timeout::Max);
+        data.len()
+    }
```

The echo-back in `receive` silently discards write errors with `let _ =`. For a sample this is acceptable, but it might be worth a brief comment or `dev_warn!` for educational purposes.

The `set_baudrate` error handling:

```rust
+        if sdev
+            .set_baudrate(...)
+            .is_err()
+        {
+            return Err(EINVAL);
+        }
```

This discards the actual baudrate returned in the `Err` variant. A more idiomatic approach would be to use `map_err` or log the actual baudrate.

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Generated by Claude Code Patch Reviewer