fix: anchored teleport

[creeperkatze]

Fixes TeleportPopoutMenu panels rendering slightly misaligned on open.

Before, the position calc read the panel's size via getBoundingClientRect(), which is transform-aware, while the panel was still mid scale-in transition, so it computed a wrong width/height and placed the panel off.

Scrolling the page then retriggered the calc, making it visibly snap into the correct spot. Now it uses offsetWidth/offsetHeight, which ignore CSS transforms, so the position is correct on the very first measurement.

[creeperkatze]

Before:

After:

[Prospector]

@Mergifyio queue

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-08-07 06:23 UTC · Rule: default · triggered by @Prospector with the @mergifyio queue command
• ✅ Checks passed · on draft merge queue: checking main (f234b7a) and #7027 together #7041
• ✅ Merged — 2026-08-07 06:29 UTC · at 9f84c0ece769f440f95e0cb677e210884634e36b

This pull request spent 5 minutes 37 seconds in the queue, including 4 minutes 58 seconds running CI.

Required conditions to merge

• github-review-approved [🛡 GitHub branch protection]
  • fix: anchored teleport #7027
• any of [🛡 GitHub branch protection]:
  • check-success = Lint and Test
  • check-neutral = Lint and Test
  • check-skipped = Lint and Test