fix: only boost editor z-index when context menu is open via :has()
Use .editor-panel:has(.context-view) to conditionally set z-index
100000 only when Monaco's context menu is present. This keeps the
center-square and other elements visible normally, but ensures the
context menu renders above everything when open.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>