[BUG] comptime AllCopyable overload specialization causes redefinition error for Copyable-constrained packs

Bug description

Problem

When Variant[*Ts] is built from a TypeList.map[...]() result,
the compiler fails to prove AllCopyable[*Ts], so Variant loses
Copyable conformance even though every element is Copyable.

oss/modular/mojo/stdlib/std/reflection/traits.mojo:41:1: error: invalid redefinition of 'AllCopyable'
comptime AllCopyable[*Ts: AnyType]: Bool = Ts.all_satisfies[
^
Included from "oss/modular/mojo/stdlib/std/reflection/__init__.mojo":1:
oss/modular/mojo/stdlib/std/reflection/traits.mojo:39:1: note: previous definition here
comptime AllCopyable[*Ts: Copyable]: Bool = True 
^

Attempted Fix

Added a specialized comptime overload in traits.mojo:
comptime AllCopyable[*Ts: Copyable]: Bool = True

However this causes a redefinition error — suggesting comptime
does not support overload specialization.

Conclusion

This appears to need a compiler-level fix rather than
a stdlib workaround.

References

• Original issue: #6498
• Attempted PR: #6504

System information

No response

Start with oss/modular/mojo/stdlib/std/reflection/traits.mojo, especially the two AllCopyable definitions and the compiler error locations. Review the context from issues #6498 and #6504, then reproduce the Variant[*Ts] case using a TypeList.map... result. Done means the compiler no longer reports a redefinition and Variant retains Copyable conformance when all elements are Copyable.