wip(13-04): checkpoint Task 3 tag-extraction work recovered after broken pipe

Verbatim checkpoint of uncommitted executor work (music/mod.rs, music/tags.rs,
mod music; in main.rs) before verification. Tests not yet run.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/archipelago/src/main.rs

@@ -61,6 +61,7 @@ mod marketplace;
 mod mesh;
 mod mesh_ports;
 mod monitoring;
+mod music;
 mod names;
 mod network;
 mod node_message;