Docs fullscreen is an in-page reading sheet under the project tabs, not the browser Fullscreen API #374

The user wanted an overlay below the tabs, not browser fullscreen, and the text at full container width (54em was rejected as too narrow). Docs.razor toggles .docs-fullscreen; app.css widens .workspace via :has(), hides tree and footer, sheet width 100% up to 1400px, font-size max(15px,.68vw).

Commits 082d8ba and 2210808, deployed 2026-10-05. The first version capped the sheet at 54em (about 810px at 15px), which the user called as narrow as beside the page tree; now width:100%;max-width:1400px (about A4 on 4K). Phone layout was confirmed good by the user. Markdown heading sizes are rem in MarkdownContent.razor.css, so fullscreen overrides them with em to scale with the sheet. Escape leaves via session.js clicking [data-docs-fullscreen-leave] unless a dialog is open. Verified with playwright-core against conderis.com: text 1161px at 1280 wide (normal view 728px), 1400px sheet at 2560 and 3840.