202609120237

Delegate kSubset semantics to KSubsetValue

TLC owns KSubsetValue, so input validation and boundary cases should be
handled there.  Pass the original set value through instead of eagerly
converting it to SetEnumValue, which rejected unenumerable sets such as Nat
and STRING.

Related to tlaplus/tlaplus Github issue #1415
https://github.com/tlaplus/tlaplus/issues/1415

[Refactor][Tests]

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Markus Alexander Kuppe <github.com@lemmster.de>