[BUG] `DType::from` rejects `S16`, `U16` and `F16`

[phil-opp]

src/core/util.rs:76-81:

impl From<u32> for DType {
    fn from(t: u32) -> Self {
        assert!(DType::F32 as u32 <= t && t <= DType::U64 as u32);
        unsafe { mem::transmute(t) }
    }
}

The upper bound is DType::U64, which is 9. But the enum continues past it (src/core/defines.rs:112-139):

    U64 = 9,
    S16 = 10,
    U16 = 11,
    F16 = 12,

So the assert fires for three of the crate's own supported types. Array::get_type() (array.rs:427-432) is the caller, which means:

let a = randu::<half::f16>(dim4!(3, 3));
let t = a.get_type();     // panics
println!("{:?}", a);      // panics — Debug impl calls get_type()

This is not a version-skew problem — it's wrong against a correct 3.8 library, and has been since f16 support was added. It's also the inverse mistake to the one in AfError::from: that assert is too loose, this one is too tight.

Fix: bound at DType::F16 as u32, or better, use an exhaustive match with a clear error for unrecognised values. Note ArrayFire 3.10 adds s8 = 13, so a match would future-proof this.

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Found by Claude Opus 5. Verified manually.