Inlines the bodies of `lyrics_get` and `lyrics_get_cache_stats` from
crate::lyrics::commands::* directly into commands_v2/legacy_compat.rs,
mapping the legacy String error type to RuntimeError::Internal at the
return boundary for v2_lyrics_get. Renames LyricsCacheStats to
V2LyricsCacheStats, hosted next to the inlined v2_lyrics_get_cache_stats.
Deletes lyrics/commands.rs entirely (also drops the dead
lyrics_clear_cache helper which had no callers; v2_lyrics_clear_cache in
commands_v2/library.rs already inlines its own logic).
The v2 functions retain their existing names, parameter shapes, and
Tauri::State signatures; only the body changes. No frontend invoke
changes required.
Step 6 of the legacy cleanup plan, group A (lyrics).
cc
vicrodh
ba878b8419