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/notifications/_index.md

@@ -0,0 +1,5 @@
+---
+theme: notifications
+heading: "Notifications"
+kind: theme
+---

todo/notifications/a-push-payload-does-not-say-which-server-sent.md

@@ -0,0 +1,16 @@
+---
+id: notifications/a-push-payload-does-not-say-which-server-sent
+title: "A push payload does not say which server sent it"
+theme: notifications
+status: open
+created: 2026-08-20
+date_source: assumed
+order: 1
+---
+
+**A push payload does not say which server sent it**, which is fine for one and breaks three things
+for several — the deep link resolves a session id against the wrong server, threading can collapse
+two servers' chats into one banner, and `mv` (a per-server catalogue hash) makes the app resync
+forever, always against whichever server pushed last. Blocks the multi-server sign-on work.
+**Settle the server identifier with that design rather than inventing one here.**
+See `docs/multi-server-push.md`.