The first attempt at R-R built a CultNetSelection with an empty (non-null)
Keys/Schemas array straight from the lowered v0 filter and handed it to the
shared evaluator. CultNetSelectionValidation.ValidateShape refuses exactly
that shape ("selection.keys is present and empty"), because for the v1 typed
door an empty list is a caller mistake. v0 and v1 read the same emptiness
differently on purpose (v0: answer nothing; v1: refuse), so v0 must decide
its answer before the selection ever reaches Validate.
CultNetDocumentRegistry.CreateRawSnapshotResponse and
CultNetDatabase.CreateShardSnapshotResponse now short-circuit to an empty
document set when the lowered schemas or keys list is present-and-empty,
without constructing a CultNetSelection or calling into the evaluator at all.
Caught by the test added in the previous commit
(CultNetDocumentRegistry_RawSnapshot_ExplicitEmptyRecordKeys_AnswersEmpty),
which failed with CultNetSelectionInvalidException before this fix. Verified
on Yggdrasil: dotnet test tests/GameCult.Networking.Tests -c Release, all
green (217 passed, 2 skipped by design).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>