- CurrentLanguage() now returns "en-GB" (fallback) instead of "" when
service is nil, consistent with other getters returning defaults
- Document why SetLanguage returns error (validates language tag) while
SetMode, SetFormality, SetDebug do not (just set values)
- Add "Does nothing if service not initialized" to Set* doc comments
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>