Dragging a session tab out of the main strip into its own zone left the
workspace alone in main. Auto treated a lone pane as "not a tab", and the
uncloseable workspace is not stranded, so main lost its tab and its "+" —
while the tile it had just split from kept a strip of its own. Two chats
side by side, one with tabs and one without, reads as "the tabs
disappeared"; ⌥⌘T only helped because it wrote an explicit `always`.
The resolver gains one input, `siblingMainZone`: on auto, a lone main tile
keeps its strip whenever another zone in the layout also hosts a main tile.
A chat that is the whole window stays chromeless, side chrome is untouched,
and an explicit `never` still wins so Hide tabs keeps working.
Both callers read it from `$mainTileZoneCount`, a computed over the tree,
the hidden set and the registry version. It is a number, so zones re-render
only when a main zone appears or goes — never per sash-drag frame — and the
store's answer (what the toggle command flips against) and the strip on
screen cannot disagree.
Austin Pickett
36010d0bba