[BUG] Cant instantiate variable of UInt256 with more than 128 bit value

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Bug description

open-source/mojo/stdlib/stdlib/builtin/_startup.mojo:114:4: error: call expansion failed
open-source/mojo/stdlib/stdlib/builtin/_startup.mojo:45:4: note: function instantiation failed
:0: note: call expansion failed
open-source/mojo/stdlib/stdlib/builtin/simd.mojo:425:8: note: function instantiation failed
:0: note: integer value 170141183460469231731687303715884105728 requires 129 bits to store, but the destination bit width is only 128 bits wide

Steps to reproduce

fn main():
    alias Uint256 = Scalar[DType.uint256]
    var a: Uint256 = 170141183460469231731687303715884105727
    a += 1
    var b: Uint256 = a #This works 
    var c: Uint256 = 170141183460469231731687303715884105728 # This does not
    print(b, c)

System information

max 25.2.0.dev2025030405

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fn main():
    var a: UInt256 = 2**256 - 1  # 115792089237316195423570985008687907853269984665640564039457584007913129639935
    var b: UInt256 = 2**255 - 1  # 115792089237316195423570985008687907853269984665640564039457584007913129639935
    # should be 57896044618658097711785492504343953926634992332820282019728792003956564819967
    var c: UInt256 = 2**64 - 1  # 115792089237316195423570985008687907853269984665640564039457584007913129639935
    # should be 18446744073709551615
    print(a == b == c)  # True should be False

System Information
max 25.2.0.dev2025030619

[soraros]

I think this is the problem

max/mojo/stdlib/src/builtin/simd.mojo

Lines 472 to 474 in a37617b

	var t0 = __mlir_op.`pop.cast_from_builtin`[
	_type = __mlir_type.`!pop.scalar<si128>`
	](tn1)