Fix song selector sorting and difficulty focus

docs/re_gc_song_select.md

@@ -26,7 +26,8 @@ What is already wired:
 - the original `common_eng` controller HUD and animated Yume navigator scenes;
 - the executable's purple-to-pink background strip, rotating wire sphere,
   translucent menu geometry, and `balloon.dds` lower backing layer;
-- genre filtering from the catalog genre byte;
+- the eight original sort tabs, with genre headings and catalog-backed title,
+  difficulty, newest and random ordering;
 - the twelve dynamically linked `mc_music_link`/`mc_index_link` carousel
   slots with their executable positions and opacity table, including original
   `s_j_eng.dds` genre headings as real scrolling entries;
@@ -48,7 +49,7 @@ Controls:
 ```text
 Up / Down, W / S       previous / next song
 PageUp / PageDown      jump by eight songs
-Q / E or Tab           genre
+Q / E or Tab           song order
 Enter or Space         enter difficulty screen
 Escape                 close selector