The rail was on the right. It now leads the row instead, so the section menu
reads as a conventional left-hand navigation column.
Which side it lands on was never a stylesheet decision: `.app-body` is a flex
row and the aside is simply its first child now, with `.app-main` after it.
The only style change that had to follow is the rail's separator, which moves
from its left edge to its right, plus the collapse tooltip's placement.
The global shell contract in base.css now says this explicitly, so the next
person to move the rail knows the side comes from DOM order rather than from a
rule in that file.
govin
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