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/_index.md

@@ -0,0 +1,20 @@
+---
+theme: plugin-repos
+heading: "Plugin repos — what writing their READMEs turned up"
+kind: theme
+---
+
+Three READMEs were written on 2026-08-16 (`music`, `offscale`, `example`) and pushed to their own repos.
+Writing them meant reading each plugin against its own documentation, which is the cheapest audit there
+is. Everything below was found that way and none of it is fixed.
+
+**Offscale is still branded headscale in shipped, user-visible places.**
+
+**Documentation that actively lies.**
+
+      **Done.** Verified 2026-08-21: zero occurrences of either name.
+
+**Conventions a plugin author has to guess.** All verified in `discover.ts`/`mount.ts`, none documented
+outside the example's new README:
+
+**Genuinely missing.**