Claude review: gpu: nova-core: add Architecture::is_pre_hopper() helper

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

Patch Review

```rust
impl Architecture {
    pub(crate) fn is_pre_hopper(self) -> bool {
        matches!(self, Self::Turing | Self::Ampere | Self::Ada)
    }
}
```

Simple and correct. The current `Architecture` enum only has Turing, Ampere, and Ada variants, so this returns `true` for all current variants. When Hopper/Blackwell are added, this will automatically return `false` for them because of the `matches!` exhaustive listing (as opposed to a negation pattern like `!matches!(self, Self::Hopper | ...)`).

**Minor:** This is arguably premature since all supported architectures are pre-Hopper, but it's good forward-thinking and the code is trivial.

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