sidebarAvailable grouped suggestionsActive() with the full-screen overlays
(setup, wizards, pickers), whose stated rationale is that they "take over the
chat column and render at full width". That is not true of the `/` palette:
suggestionOverlay draws it through centerRenderedBlock at
minInt(width, suggestionPaletteMaxWidth), a centred box capped at 76 cells
floating over the chat column.
Treating it as full-screen collapsed the whole layout on every `/`: the sidebar
disappeared, the plan panel dropped out of it and re-rendered inline above the
composer, and the transcript re-wrapped to full width -- a jarring reflow for a
popup, and worst mid-run with a live plan on screen.
It cannot overlap the sidebar either: twoColumnTranscriptView renders the
overlay with width = chatColumnWidth, so the palette is capped at
min(chatColumn, 76) and centred inside the chat column. Mouse hit-testing is
unaffected because sidebarLineAtMouse carries its own suggestionsActive() guard,
so clicks still reach the palette rather than the sidebar rows beneath it.
The genuinely full-width overlays keep suppressing the sidebar, pinned by the
new test alongside the palette case.