feat(desktop): quick-create profile from rail + pin rail on empty sidebar

- Add a "+" in the profile rail that opens a self-contained CreateProfileDialog
  (name + clone toggle + optional SOUL.md); extract it and ActionStatus from
  the profiles view so both surfaces share one flow.
- Keep the profile rail pinned to the bottom when a profile has no sessions by
  rendering a flex-1 spacer (previously the rail floated up to the nav).

apps/desktop/src/components/ui/action-status.tsx

@@ -0,0 +1,25 @@
+import type { ReactNode } from 'react'
+
+import { Check, Loader2 } from '@/lib/icons'
+
+// idle → saving → done label+icon for action buttons (create / rename / delete…).
+export function ActionStatus({
+  state,
+  idle,
+  busy,
+  done,
+  idleIcon = null
+}: {
+  state: 'done' | 'idle' | 'saving'
+  idle: string
+  busy: string
+  done: string
+  idleIcon?: ReactNode
+}) {
+  return (
+    <>
+      {state === 'saving' ? <Loader2 className="size-4 animate-spin" /> : state === 'done' ? <Check /> : idleIcon}
+      {state === 'saving' ? busy : state === 'done' ? done : idle}
+    </>
+  )
+}