Claude review: gpu: nova-core: gsp: fix stale doc comments on command queue methods

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

Patch Review

**Status: Looks good**

A straightforward documentation cleanup. The changes are:

1. Adding missing `EMSGSIZE` error doc:
```
+    /// - `EMSGSIZE` if the command exceeds the maximum queue element size.
```
This was presumably missing from the original docs — good to add.

2. Updating `receive_msg` docs to accurately describe current behavior:
```
-    /// `init` is a closure tasked with processing the message...
+    /// The expected message type is specified using the `M` generic parameter. If the pending
+    /// message has a different function code, `ERANGE` is returned and the message is consumed.
```
The old docs referenced a closure-based API that no longer exists. The replacement accurately describes the current generic-parameter approach.

3. Updating error code documentation:
```
-    /// - `EINVAL` if the function of the message was unrecognized.
+    /// - `EINVAL` if the function code of the message was not recognized.
+    /// - `ERANGE` if the message had a recognized but non-matching function code.
```
The `EAGAIN` → `ERANGE` distinction and the addition of `ERANGE` docs are correct.

4. Adding note about error propagation:
```
+    /// Error codes returned by [`MessageFromGsp::read`] are propagated as-is.
```

5. Removing the "this design is by no means final" comment — appropriate for a maturing codebase.

No issues. Already has Reviewed-by from Zhi Wang.

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