[BUG] [BUG] cute.arch.store doesn't work with fp8 vector #3712

# CuTeDSL MRE: cute.arch.store of an fp8 vector fails in the NVVM backend.
#
# cute.arch.store documents `val` as "scalar Numeric or vector ir.Value". An
# f32 / bf16 / u8 / i8 TensorSSA stores fine (one st.global.v8.b32), but an
# fp8 one (x.to(Float8E4M3FN) or Float8E5M2) traces and then fails while
# lowering:
#   LLVM Translation failed for operation: builtin.unrealized_conversion_cast
# Not a bit-width issue: the same fp8 vector bitcast to Uint8 stores fine.
#
# Compile-only; prints one line per variant.
#   python arch_store_fp8_vector.py
import importlib.metadata

import cutlass
import cutlass.cute as cute
from cutlass import BFloat16, Float8E4M3FN, Float8E5M2, Float32, Int8, Uint8

N = 32  # elements per thread


def make(dtype, via_u8):
    @cute.kernel
    def kernel(out: cute.Tensor):
        tid, _, _ = cute.arch.thread_idx()
        x = cute.make_rmem_tensor(N, Float32)
        for i in cutlass.range_constexpr(N):
            x[i] = Float32(tid + i)
        v = x.load().to(dtype)
        dst = out[tid, None].iterator
        if cutlass.const_expr(via_u8):
            cute.arch.store(cute.recast_ptr(dst, dtype=Uint8), v.bitcast(Uint8))
        else:
            cute.arch.store(dst, v)

    @cute.jit
    def run(out: cute.Tensor):
        kernel(out).launch(grid=(1, 1, 1), block=(32, 1, 1))

    return run


print("nvidia-cutlass-dsl", importlib.metadata.version("nvidia-cutlass-dsl"))
for dtype, via_u8 in (
    (Float32, False),
    (BFloat16, False),
    (Uint8, False),
    (Int8, False),
    (Float8E4M3FN, False),
    (Float8E5M2, False),
    (Float8E4M3FN, True),
):
    t = cute.runtime.make_fake_tensor(dtype, (32, N), stride=(N, 1), assumed_align=32)
    name = f"{dtype.__name__:13s} {'bitcast->u8' if via_u8 else 'direct'}"
    try:
        cute.compile(make(dtype, via_u8), t)
        print(f"  {name}: ok")
    except Exception as e:  # noqa: BLE001
        msg = " ".join(str(e).split())
        key = "unrealized_conversion_cast"
        print(f"  {name}: FAILED ({key if key in msg else msg[:200]})")