fix: restore Escape key support in LayoutShell (was overwritten by other task)

app/src/lib/collapsible-context.tsx

@@ -0,0 +1,32 @@
+"use client";
+import { createContext, useContext, useState, type ReactNode } from "react";
+
+/**
+ * Shared context for tracking which CollapsibleSection is currently open.
+ * Used by LayoutShell to implement Escape-to-close across all panels.
+ */
+
+interface CollapsibleContextValue {
+  /** The id of the currently open section, or null if all are collapsed */
+  openSectionId: string | null;
+  /** Set the open section. Pass null to close all. */
+  setOpenSectionId: (id: string | null) => void;
+}
+
+const CollapsibleContext = createContext<CollapsibleContextValue>({
+  openSectionId: null,
+  setOpenSectionId: () => {},
+});
+
+export function CollapsibleProvider({ children }: { children: ReactNode }) {
+  const [openSectionId, setOpenSectionId] = useState<string | null>(null);
+  return (
+    <CollapsibleContext.Provider value={{ openSectionId, setOpenSectionId }}>
+      {children}
+    </CollapsibleContext.Provider>
+  );
+}
+
+export function useCollapsibleContext() {
+  return useContext(CollapsibleContext);
+}