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>

docs/DESIGN.md

@@ -18,7 +18,7 @@ decides something new, add it under "Decisions" with the date.
 - **Copy and paste of builds.** Pasting places ghosts that the bot builds from the bag.
 - **Tool upgrades are earned in a satisfying, not tedious way**, not bought with arbitrary
   credits. So far that means casting them: a drill bit in a Bit mold, a bigger bag in a Tank mold.
-  The owner wants the whole upgrade system redesigned (see NOTES.md).
+  The owner wants the whole upgrade system redesigned (task t14).
 - **A hovering bot that flies freely.** A limited bag that can be upgraded.
 - **An economy instead of a rocket or other final goal.**
   - Sell materials at the trade dock; refined goods and alloys pay more.
@@ -165,7 +165,8 @@ above, including:
   refiners until none is left. The owner's reason: it is less profitable than making glass, so
   players will do it only when they need more ore rather than more money.
 - The project moved from a claude.ai artifact to local development with coding agents. It is
-  built from small files, with `NOTES.md` as the owner's to-do inbox.
+  built from small files, with `NOTES.md` as the owner's to-do inbox (since 2026-10-24, a
+  kandown board in `tasks/`).
 - **Replace is held G, not Ctrl.** The owner hit the browser's Ctrl+W (close tab) and Ctrl+D
   (bookmark) while replacing and flying with WASD, and the game ignored WASD while Ctrl was held.
 
@@ -200,9 +201,14 @@ above, including:
   list loads, renames and deletes them, and a new or imported world never overwrites another. An
   old single save becomes 'World 1'. The owner asked for multiple saves.
 
+**2026-10-24:**
+- **The to-do list is a kandown board.** `NOTES.md` became one task file per note in
+  `tasks/` (Todo for tasks, Backlog for discussions and ideas, Review for "done, please check").
+  The owner wanted a task tool built for AI agents.
+
 ## Ideas not built yet
 
 - **Concrete**, as a stronger wall material from rubble.
 - **Upgrade ideas for the drill**: an amplifier, a tuning fork, harmonics. Also a Grav pick
   upgrade tool and mining charges. See `docs/systems/dig-tools.md`.
-- The owner's ideas for later are in the "Future features and ideas" section of `NOTES.md`.
+- The owner's ideas for later are tasks tagged `idea` in the Backlog of the task board.