perf(tree): Lazily initialize event buffer

[Josmithr]

Most nodes likely don't get any event subscriptions. Lazy initialization avoids unnecessary allocations and internal event registrations..

[github-actions]

Hi! Thank you for opening this PR. Want me to review it?

Based on the diff (87 lines, 2 files), I've queued these reviewers:

• Correctness — logic errors, race conditions, lifecycle issues
• Security — vulnerabilities, secret exposure, injection
• API Compatibility — breaking changes, release tags, type design
• Performance — algorithmic regressions, memory leaks
• Testing — coverage gaps, hollow tests

How this works

• Adjust the reviewer set by ticking/unticking boxes above. Reviewer toggles alone don't trigger anything.

• Tick Start review below to dispatch the review fleet.

• After review finishes, tick Start review again to request another run — it auto-resets after each dispatch.

• This comment updates as new commits land; your reviewer selections are preserved.

• Start review

[noencke]

Nice!

[Copilot]

Pull request overview

This PR optimizes simple-tree node event handling by lazily allocating the per-node kernel event buffer, reducing allocations and internal event wiring for nodes that never receive event subscriptions.

Changes:

• Lazily initialize TreeNodeKernel’s internal KernelEventBuffer on first access to kernel.events, and migrate the source on hydration only if the buffer exists.
• Add runtime protection against subscribing on a disposed event buffer.
• Extend treeNodeKernel tests to cover hydration with pre-registered listeners, disposed-node subscription behavior, and subscribe/unsubscribe behavior within withBufferedTreeEvents.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
packages/dds/tree/src/test/simple-tree/core/treeNodeKernel.spec.ts	Adds regression tests covering lazy buffer allocation edge cases across hydration, disposal, and buffered scopes.
packages/dds/tree/src/simple-tree/core/treeNodeKernel.ts	Implements lazy KernelEventBuffer creation and conditional migration/disposal logic; adds an assertion guarding event registration on disposed buffers.

[noencke]

Why doesn't this also use this.assertNotDisposed()?