Right sidebar reads as ONE panel: fleet section stretches to the panel width

The sub-agents fleet panel was a w-64 fixed aside with no left edge —
aligned with the plan panel only by coincidence in list mode, floating
detached in rail (w-10) and graph (w-96) modes. It now stretches to the
sidebar column's current width and shares the panel's border-l, so the
sidebar is one continuous panel with SUB-AGENTS above PLAN (thin border-b
divider). Verified headlessly in list and graph mode: identical edges and
widths (256/256 and 384/384), perfect vertical stack (fleet 0..99.5, tree
99.5..800), no overlap, 9-node graph intact.

The rail-mode-while-jobs-run question (fleet cards would cram into w-10)
is logged as wave-2 UX design work for the UI stream.

components/sub-agents-panel.tsx

@@ -26,7 +26,7 @@ export function SubAgentsPanel({ jobs }: { jobs: JobRecord[] }) {
 	return (
 		<aside
 			data-testid="sub-agents-panel"
-			className="flex w-64 shrink-0 flex-col border-b border-border/60 bg-card/30 px-3 py-2.5"
+			className="flex w-full shrink-0 flex-col border-b border-l border-border/60 bg-card/30 px-3 py-2.5"
 		>
 			<div className="flex items-center gap-2 text-[11px] font-medium uppercase tracking-wide text-muted-foreground">
 				<BotIcon className="size-3.5" />