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/transmission/files-tab-on-huge-torrents.md

@@ -0,0 +1,13 @@
+---
+id: transmission/files-tab-on-huge-torrents
+title: "Files tab on huge torrents"
+theme: transmission
+status: open
+created: 2026-08-20
+date_source: assumed
+order: 3
+---
+
+**Files tab on huge torrents.** `detail/FilesTab.tsx` builds the whole tree and renders every
+node — no virtualisation. Fine at 14 files; unknown at a few thousand. If it stalls, the fix is
+`useVirtualizer` over a flattened visible-node list, the same shape as `TorrentTable`.