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/multi-user/deprovisionosaccount-is-written-but-has-never.md

@@ -0,0 +1,18 @@
+---
+id: multi-user/deprovisionosaccount-is-written-but-has-never
+title: "`deprovisionOsAccount` is written but has never run against a real account"
+theme: multi-user
+status: open
+created: 2026-08-12
+date_source: stated
+order: 2
+---
+
+**`deprovisionOsAccount` is written but has never run against a real account.** Landed 2026-08-12 in
+`os-user-deprovision.ts` and wired into `deleteUserHandler`, which now refuses to delete the row when
+the Linux teardown fails — so a failure is retryable instead of forgotten. Only the pure guards
+(`guardDeletable`, `guardMemberTree`, `parseSubUidEntry`) have tests; the reap loop, the `chown -R`
+sever and `userdel` have been exercised by nobody. `docs/deprovision-os-account.md` → "What is still
+unproven" has the five-step validation, and it has to happen on the production host with a throwaway
+account that has **a shell left open** and **a container writing as a non-root user** — those are the
+two cases the quiet path passes vacuously.