[OPIK-5360] [FE] fix: collapse ResizableSidePanel width when closed to prevent scroll overflow

[andriidudar]

Details

Fix horizontal scroll showing a blank page when scrolling all the way to the right on any page with a table (Projects, Experiments, Datasets).

The ResizableSidePanel portal wrapper uses absolute inset-0, giving it full viewport width even when closed. While pointer-events-none blocked interactions, the element still contributed to the document's scrollable width. Adding w-0 when the panel is closed collapses the wrapper so it no longer extends the scroll area.

Change checklist

• User facing
• Documentation update

Issues

• OPIK-5360

AI-WATERMARK

AI-WATERMARK: yes

• Tools: Claude Code
• Model(s): Claude Opus 4.6
• Scope: assisted (validation of user's fix)
• Human verification: code review + manual testing

Testing

• Go to any page with a scrollable table (Projects, Experiments, Datasets)
• Scroll all the way to the right — verify no blank page appears
• Open a side panel (e.g. click a trace row) — verify it opens and renders correctly
• Resize the side panel — verify drag handle works
• Close the side panel — verify it closes with smooth animation
• Verify arrow key navigation still works within the side panel

Documentation

N/A

[github-actions]

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[github-actions]

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