todo: one file per item, grouped by theme, with a generated index

TODO.md had reached 1050 lines and 72 open items across 28 sections, read mostly
on a phone. It is now a directory: todo/<theme>/<item>.md, one card per file, with
frontmatter carrying id, status, created date and order, and the prose body copied
across verbatim. TODO.md becomes a generated index (bun run todo:index).

Dates: where an item's prose stated one it is used; otherwise its old section's;
otherwise 2026-08-20, floored at the day before the split rather than invented.
date_source records which.

Shaped for a two-way Kanban board, filed as todo/tooling — a card is a file, id is
the identity, frontmatter is the machine's half and the body is the owner's.

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

todo/plugin-repos/plugins-music-musicapi-md-says-favourites-and.md

@@ -0,0 +1,14 @@
+---
+id: plugin-repos/plugins-music-musicapi-md-says-favourites-and
+title: "`plugins/music/MUSIC_API.md` says favourites and now-playing are served by the platform from Postgres; the sidecar serves them itself, scoped by `X-Officer-User`"
+theme: plugin-repos
+status: open
+created: 2026-08-20
+date_source: assumed
+order: 8
+---
+
+`plugins/music/MUSIC_API.md` says favourites and now-playing are served by the platform from
+Postgres; the sidecar serves them itself, scoped by `X-Officer-User`. It also documents the playlist
+item key as `<albumRel>/<file>` while the schema and favourites use the home path — the same file
+contradicts itself.