fix(desktop): render full sidebar content in hover-reveal overlay

The hover-reveal overlay showed only the nav rail — session rows, search,
pinned/recents were gated behind `sidebarOpen` (false while collapsed), so
they never mounted in the floated panel.

Add a $sidebarRevealed store the PaneShell overlay drives via a new
onHoverRevealChange callback, and gate ChatSidebar's content on
`sidebarOpen || sidebarRevealed` (contentVisible) instead of raw open
state. The overlay now shows the complete sidebar.

apps/desktop/src/components/pane-shell/pane-shell.tsx

@@ -39,6 +39,8 @@ export interface PaneProps {
    * track stays at 0px.
    */
   hoverReveal?: boolean
+  /** Called with the reveal state whenever a collapsed hoverReveal pane floats in/out. */
+  onHoverRevealChange?: (revealed: boolean) => void
   id: string
   maxWidth?: WidthValue
   minWidth?: WidthValue
@@ -205,6 +207,7 @@ export function Pane({
   id,
   maxWidth,
   minWidth,
+  onHoverRevealChange,
   resizable = false,
   width
 }: PaneProps) {
@@ -248,6 +251,12 @@ export function Pane({
     }
   }, [overlayActive, hoverRevealed])
 
+  // Surface the effective reveal state to consumers (e.g. so the sidebar can
+  // render its full content while floated, not just while the track is open).
+  useEffect(() => {
+    onHoverRevealChange?.(overlayActive && hoverRevealed)
+  }, [onHoverRevealChange, overlayActive, hoverRevealed])
+
   const startResize = useCallback(
     (event: ReactPointerEvent<HTMLDivElement>) => {
       const paneWidth = paneRef.current?.getBoundingClientRect().width ?? 0