Fix freeze from useBoxMetrics layout listener recursion

[msfeldstein]

Summary

• We have been seeing freezes when you have a component that uses the results of useBoxMetrics to adjust layout. We fixed them at the app level, but it shouldn't be so easy to have a react component completely freeze the app
• Defer layout listener callbacks out of React's resetAfterCommit stack so layout listeners (e.g. useBoxMetrics) can't synchronously schedule React state while React is still committing.
• Coalesce pending listeners and skip any listener removed before the deferred flush.
• Add a regression test plus a runnable example.

Problem

emitLayoutListeners runs from Ink's resetAfterCommit host callback. It invokes listeners synchronously, so a listener that schedules state (useBoxMetrics calls setMetrics/setHasMeasured) updates React mid-commit. When the rendered layout depends on the measured layout, each commit re-measures and re-commits, recursing until React trips its nested-update guard and throws Maximum update depth exceeded, freezing the CLI.

React commit
  -> resetAfterCommit(root)
  -> emitLayoutListeners(root)
       before: listener() immediately -> hook setState during commit -> nested update -> commit -> ... (recurses past React's limit)
       after:  queue listener for microtask -> commit finishes -> listener runs if still subscribed

Fix

Buffer listeners into a pending set and flush them once in a queueMicrotask after the commit unwinds. The flush re-checks subscription so a listener removed in the window between commit and flush (e.g. an unmounting component) does not fire.

Test plan

• npx ava test/dom-layout-listeners.tsx — new regression test renders a layout-feedback box and asserts render does not throw. Verified it fails without the fix (Maximum update depth exceeded) and passes with it.
• npx ava test/use-box-metrics.tsx
• npx tsc --noEmit
• npx prettier --check
• Manual repro: node --import=tsx examples/layout-listener-recursion/index.ts crashes without the fix, converges with it.

Made with Cursor

[sindresorhus]

I don't think this is fixed yet.

• The existing useBoxMetrics sibling-content behavior regresses for me on this branch. npx ava test/use-box-metrics.tsx -m "updates when sibling content changes" fails consistently on the PR branch and passes on master. Since useBoxMetrics is supposed to update when sibling/content changes, deferring every emitLayoutListeners call looks like it can delay or miss a supported update. Maybe only the commit-time path should be deferred, or the hook needs another way to keep this update synchronous enough for the existing contract.
• The new regression test is not catching the warning. Running node --import=tsx examples/layout-listener-recursion/index.ts still prints Maximum update depth exceeded, even though the new AVA test passes. So this avoids the hard crash, but it still hits React's nested-update guard. The test should fail on that warning, otherwise teh repro can regress silently.