fix(dashboard): portal floating windows to body; board pop-out returns to board

- FloatingWindow renders via createPortal(document.body) so it escapes every ancestor stacking context — card dependency/overlap badges and the List view's sticky sort header + column divider no longer paint over the modal (4000+ z-index now wins page-wide).
- Popping out a task detail from the board's full-panel view also returns the main panel to the board, so the board sits behind the floating window.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/dashboard/app/App.tsx

@@ -2067,7 +2067,8 @@ function AppInner() {
                 Board-card detail (full main panel) renders its "Back to board" affordance inside TaskDetailContent's gray header (far right, across from the task id) instead of a separate back-row above the content. The prop only renders the header back button when both embedded and onBackToBoard are present, so ListView split-pane and modal usages stay unaffected.
                 */
                 onBackToBoard={closeTaskDetailMainPanel}
-                onPopOut={popOutTaskDetail}
+                /* FNXC:FloatingWindow 2026-06-22-21:10: Popping out from the board's full-panel detail also returns the main panel to the board, so the board (not the emptied detail) sits behind the floating window. */
+                onPopOut={(task) => { popOutTaskDetail(task); closeTaskDetailMainPanel(); }}
                 onOpenDetail={(value) => setMainPanelDetailTask(value)}
                 onMoveTask={moveTask}
                 onDeleteTask={deleteTask}

packages/dashboard/app/components/FloatingWindow.tsx

@@ -7,6 +7,7 @@ import {
   type PointerEvent as ReactPointerEvent,
   type ReactNode,
 } from "react";
+import { createPortal } from "react-dom";
 import { X } from "lucide-react";
 import "./FloatingWindow.css";
 
@@ -268,7 +269,11 @@ export function FloatingWindow({
     zIndex,
   } as CSSProperties;
 
-  return (
+  /*
+  FNXC:FloatingWindow 2026-06-22-21:10:
+  Rendered via a portal to document.body so the window escapes every ancestor stacking context (board card badges, the List view's sticky sort header + column divider, transformed columns, etc.). Without the portal the panel's z-index battles inside whatever subtree mounted it, letting card dependency/overlap tags and the list divider/sort header paint over the modal. At document.body the 4000+ z-index wins over all page content.
+  */
+  return createPortal(
     <div
       className="floating-window-overlay"
       role="dialog"
@@ -312,6 +317,7 @@ export function FloatingWindow({
           {children}
         </div>
       </div>
-    </div>
+    </div>,
+    document.body,
   );
 }