KnownListBuilder.MineCopyTokens resolves a copy add's baseIdx against the
actor's own idx->cardId map (self/other by isSelf), yielding (idx,cardId,
isSelf). Skips concrete/choice adds, string (private-group) baseIdx, and
unknown sources (degrade). Third token-reveal slice.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>