Sessions are laid out in as many columns as let the fit show them
largest, in balanced columns, instead of one column several screens
tall. A session that starts later takes a hole, a column's foot or a new
column, whichever keeps the board largest, and a subagent lands beside
its session as it sits now. The machine and usage panels' strip is left
out of both the layout and the fit, so no column hides under them. Icon
buttons answer the pointer near the glyph, not only on it. Also in this
release: a paired deck's dialog draws what goes each way.

Release notes: two entries, chosen at the release gate.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>