Move the to-do list from NOTES.md to a kandown board

Each note is a task in tasks/ with the owner's words under ## Context; the
board rules are in .kandown/kandown_work.md and docs/kandown.md explains how
kandown works here.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -5,5 +5,6 @@
 - To look at a screenshot, open the PNG with the Read tool. Do this every time you change
   anything drawn, and before you call it done.
 - Use WebSearch and WebFetch for anything outside this repository, per the honesty rules above.
-- Keep `docs/agent-log.md`, `NOTES.md` and `docs/PROJECT_MAP.md` current, as described above.
+- Keep `docs/agent-log.md`, the task files in `tasks/` and `docs/PROJECT_MAP.md` current, as
+  described above.
   They are how the next session, yours or another agent's, picks up the work.