fix(web): keep image preview above sidebar control

[maria-rcks]

The expanded image backdrop shared z-50 with the global sidebar control, which renders later and stayed undimmed above the overlay. This moves the preview to z-[60], above app chrome and below toast and popover layers. Full CI is green; visual after evidence is pending browser approval. Built with gpt-5.6-sol through the Codex harness.

Before:

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Note

Low Risk
Single z-index tweak in a presentation component with no auth, data, or business-logic impact.

Overview
Fixes expanded chat image/video preview appearing under the global sidebar/workspace chrome because both used z-50.

Raises the ExpandedImageDialog backdrop from z-50 to z-[60] so the dimmed full-screen overlay and preview sit above those fixed controls while staying below higher UI layers (e.g. composer at z-[70]).

^{Reviewed by Cursor Bugbot for commit 57676f3. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Raise ExpandedImageDialog overlay z-index from z-50 to z-[60]

Changes the top-level dialog div in ExpandedImageDialog.tsx so the image preview renders above the sidebar control. The overlay now sits at stacking order 60.

^{Macroscope summarized 57676f3.}

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[macroscopeapp]

Approvability

Verdict: Approved at 57676f3

Macroscope's review found this PR approvable — This is a narrowly scoped UI fix that changes only the expanded image dialog’s stacking order, placing it above the existing sidebar control without affecting application data or workflows. It does not change product defaults or introduce a new capability.

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