webgl tests broken/incomplete

[jerch]

@Tyriar

With #5852 the following webgl addon tests are wonky or literally wrong (testing for DOM nodes?), thus currently deactivated:

• [Chromium] › test/playwright/SharedRendererTests.ts:172:7 › WebGL Renderer Integration Tests › background 0-15 invisible
• [Chromium] › test/playwright/SharedRendererTests.ts:338:7 › WebGL Renderer Integration Tests › background 16-255 invisible
• [Chromium] › test/playwright/SharedRendererTests.ts:718:7 › WebGL Renderer Integration Tests › background true color grey invisible
• [Chromium] › test/playwright/SharedRendererTests.ts:875:9 › WebGL Renderer Integration Tests › minimumContrastRatio › should enforce half the contrast for dim cells
• [Chromium] › test/playwright/SharedRendererTests.ts:1180:9 › WebGL Renderer Integration Tests › regression tests › Invisible text is visible in the DOM renderer #4758: multiple invisible text characters without SGR change should not be rendered
• all webgl tests on safari (kinda all broken in CI)
• all webgl tests on firefox (passes locally, but not in CI)

Also see #5852.

[longshuaige]

Update after testing with the merged PR #5883:

Significant improvement — the severe ghosting that previously accumulated during long sessions is now much harder to reproduce. The fix clearly works.

However, there are still mild residual symptoms in edge cases:

• After long streaming sessions (e.g. Claude Code outputting mixed CJK/Latin text), I occasionally see light character ghosting on a few cells.
• Scrolling the viewport by one line or selectiion error char immediately clears it.
• Selecting the affected text also clears it.

Environment: Tauri/WKWebView on macOS stable, devicePixelRatio=2, allowTransparency: true, transparent theme background.

@vsych @Tyriar — should I open a separate follow-up issue for this residual behavior, or keep tracking it here?

Thanks

[Tyriar]

@longshuaige don't suppose you could try put together a reliable repro on the demo, ideally on chrome? Bit hard with cc as I don't have a sub. The smaller and more reliable the easier it is to fix