Claude review: gpu: nova-core: gsp: add reply/no-reply info to `CommandToGsp`

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

Patch Review

This is the core design patch. Adds `type Reply` to the `CommandToGsp` trait and a `NoReply` marker type:

```rust
pub(crate) struct NoReply;
```

The approach is sound. Commands that don't expect a reply use `type Reply = NoReply`, and the `send_command_no_wait` function enforces this at the type level with:

```rust
M: CommandToGsp<Reply = NoReply>,
```

The `send_command` method now returns `Result<M::Reply>` and includes the receive loop:

```rust
pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result<M::Reply>
where
    M: CommandToGsp,
    M::Reply: MessageFromGsp,
    ...
{
    self.send_command_internal(bar, command)?;
    loop {
        match self.receive_msg::<M::Reply>(Self::RECEIVE_TIMEOUT) {
            Ok(reply) => break Ok(reply),
            Err(ERANGE) => continue,
            Err(e) => break Err(e),
        }
    }
}
```

**Concern**: The `Err(ERANGE) => continue` loop has no bound. If the GSP keeps sending non-matching messages, this loops forever. Each iteration does have a `RECEIVE_TIMEOUT` on the individual receive, so it won't literally spin forever — eventually `receive_msg` will return `ETIMEDOUT` if no messages arrive. But if a stream of wrong-function-code messages keeps arriving, the loop will consume them all indefinitely without ever timing out. In practice this is unlikely, but a maximum iteration count or an overall deadline would be safer. This is a pre-existing pattern from the old code, so not a regression — but worth noting as a future improvement since this loop is now in a more prominent, reusable position.

The `SplitCommand` correctly propagates `type Reply = C::Reply` (line 951), which is correct since the split command should have the same reply type as the original.

The update to `get_gsp_info` is a nice simplification, collapsing the function to a single line.

The `ContinuationRecord` and test `TestPayload` correctly use `type Reply = NoReply` since continuation records don't receive individual replies.

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Generated by Claude Code Patch Reviewer