Language::Es was registered and switches formulas to Spanish (SUMA, decimal comma, semicolon
arguments), but every interface label still fell back to English. This adds es.rs with all 266
labels in Excel's Spanish wording (Combinar y centrar, Inmovilizar paneles, Análisis de
hipótesis, Buscar objetivo, Rastrear precedentes…) and covers Spanish in the i18n tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012JC2QZ1Qc5KQMBswS38GKy
