Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

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### Issue 1 of 2
packages/ui/src/features/canvas/hooks/useTaskChannelMap.ts:30-40
**`useMemo` dependency is always stale due to `channels` reference instability**

`useChannels` computes the `channels` array inline — `filter(...).map(...).sort(...)` — without memoizing it, so every render of `useChannels` produces a new array reference even when the underlying data hasn't changed. Because `channels` is in the `useMemo` dependency array here, the Map is rebuilt on every render while the menu is open. That rebuilt Map is a new reference, so `taskSections` in `CommandMenu` also recomputes on every render. With a small channel count and a short open-window this rarely matters in practice, but the cascade is worth closing. Using the `combine` option on `useQueries` to fold `channels` into the result in a stable way, or memoizing `channels` inside `useChannels`, would break the chain.

### Issue 2 of 2
packages/ui/src/features/command/CommandMenu.tsx:98-99
**Dual `useChannels` subscriptions — one always-on, one gated**

`CommandMenu` subscribes to `useChannels()` at line 98 (always enabled) and `useTaskChannelMap({ enabled: open })` internally also calls `useChannels({ enabled: open })`. The two subscriptions share the same React Query cache key so no extra network requests occur, but there are now two live subscriptions returning independently-computed (new-reference-each-render) arrays from the same underlying data. Passing the already-fetched `channels` into `useTaskChannelMap` as a parameter would remove the internal `useChannels` call, make the hook's inputs explicit, and resolve the reference-instability cascade noted on the hook itself.