Dynamic sizes lit demo crashes/ loads very slowly

Describe the bug

Your demo with the latest versions of lit-virtual (3.13.29) and virtual-core (3.17.0) either loads very slowly (> 1 minute) or just crashes the browser.

I was really happy a new version was available, because 3.16 (and some versions before) broke the scrollToIndex functionality in Lit, but this release might unfortunately be worse.
Once the page actually loads the scrollToIndex does seem to work 😁

Your minimal, reproducible example

https://stackblitz.com/edit/vitejs-vite-wvfdjawc?file=package.json,index.html,tsconfig.json,src%2Fmain.ts&terminal=dev

Steps to reproduce

I isolated the RowVirtualizerDynamic scenario and removed the other 2 that were on the page.
There is no real reproduction path, just try to load the page.

It can take over a minute for the page to load sometimes. And sometimes the browser just crashes.

Expected behavior

The page loads fast and the scrolling to halfway works.

How often does this bug happen?

Often

Screenshots or Videos

No response

Platform

MacOS 26.5
Chrome 148.0.7778.215
Firefox 148.0.7778.215

tanstack-virtual version

3.17.0

TypeScript version

5.6.3

Additional context

@tanstack/lit-virtual": "3.13.29"

I removed the generation of random paragraphs with faker and just have every item be the same string, that didn't solve anything.

Terms & Code of Conduct

• I agree to follow this project's Code of Conduct
• I understand that if my bug cannot be reliable reproduced in a debuggable environment, it will probably not be fixed and this issue may even be closed.

Start with the StackBlitz reproduction, especially package.json and src/main.ts, and run the isolated RowVirtualizerDynamic scenario in the listed browser versions. Compare loading and scrollToIndex behavior with the reported lit-virtual 3.13.29 and virtual-core 3.17.0 versions. Done means the page loads promptly, does not crash the browser, and scrolling halfway works.