Performance Issue: Visible long sustain notes cause a memory leak in the Chart Editor

[Hundrec]

Issue Checklist

• I have read the Contributing Guide
• I have checked the Issues/Discussions pages to see if my issue has already been reported
• I have properly titled my issue

Platform

Itch.io (Downloadable Build) - Windows

Browser

None

Version

0.6.4

Description (include any images, videos, errors, or crash logs)

This always happens with long sustain notes, but only sometimes with short sustain notes.

This is similar to #5012, but happens when hold notes are simply in view rather than when you're dragging them.

The memory rapidly increases during both scrolling and playback, as long as the trail is in view.

See the video of a long sustain in Cocoa Erect's chart below.

chart.editor.sustain.memory.leak.mp4

Steps to Reproduce

1. Enable the RAM debug display
2. Open the Chart Editor
3. Choose a song with a relatively long sustain note (8-12 steps will probably do)
4. Scroll it in and out of your view

[Lasercar]

I've noticed this starts happening when you select a hold note, then select and move another one, and it's because the selection box duplicates:

2025-05-30.19-45-25.mp4

So this is either very related to #5064 or a duplicate, and fixed by the same PR.

[Lasercar]

2025-05-30.19-52-14.mp4

It's fixed by #5073

[github-actions]

This issue is a duplicate. Please direct all discussion to the original issue.