fix: sidebar workspace tree collapses on navigation

Root cause: sectionsOpen did not include workspace:true by default,
and toggle state was not persisted. On every page navigation,
sectionsOpen.workspace defaulted to undefined (falsy), hiding the
workspace tree section.

Fixes:
- sectionsOpen now defaults with workspace:true
- sectionsOpen persisted to localStorage on toggle and before navigation
- beforeunload handler auto-saves expandedFolders + sectionsOpen
  (covers <a href> navigation for file clicks too)
- navigateToFolder saves both expandedFolders and sectionsOpen

app/templates/base.html

@@ -496,8 +496,19 @@
       favoriteIds: new Set([{% for p in favorite_pages %}'{{ p.id }}'{% if not loop.last %},{% endif %}{% endfor %}]),
 
       // ── Sections collapsible ──
-      sectionsOpen: { recents: true, private: true, meetings: true, favorites: true, agents: true, shared: true, apps: true },
-      toggleSection(key) { this.sectionsOpen[key] = !this.sectionsOpen[key]; this.sectionsOpen = Object.assign({}, this.sectionsOpen); },
+      sectionsOpen: (function() {
+        var def = { recents: true, private: true, meetings: true, favorites: true, agents: true, shared: true, apps: true, workspace: true };
+        try {
+          var saved = JSON.parse(localStorage.getItem('fd_sections') || '{}');
+          return Object.assign(def, saved);
+        } catch(e) { return def; }
+      })(),
+      toggleSection(key) {
+        this.sectionsOpen[key] = !this.sectionsOpen[key];
+        this.sectionsOpen = Object.assign({}, this.sectionsOpen);
+        try { localStorage.setItem('fd_sections', JSON.stringify(this.sectionsOpen)); }
+        catch(e) {}
+      },
       toggleWorkspaceMenu() {
         if (window.innerWidth <= 768) {
           this.mobileSidebarOpen = !this.mobileSidebarOpen;
@@ -814,9 +825,11 @@
         catch(e) {}
       },
       navigateToFolder(id) {
-        // Save expansion state before navigating
-        try { localStorage.setItem('fd_expanded_folders', JSON.stringify(this.expandedFolders)); }
-        catch(e) {}
+        // Save expansion + sections state before navigating
+        try {
+          localStorage.setItem('fd_expanded_folders', JSON.stringify(this.expandedFolders));
+          localStorage.setItem('fd_sections', JSON.stringify(this.sectionsOpen));
+        } catch(e) {}
         window.location = `/local-workspace?folder=${id}`;
       },
 
@@ -841,6 +854,18 @@
       }
     };
   }
+
+  // Auto-save sidebar state before navigation (covers <a href> clicks)
+  window.addEventListener('beforeunload', function() {
+    try {
+      var el = document.querySelector('[x-data]');
+      if (el && el.__x) {
+        var data = el.__x.$data;
+        if (data.expandedFolders) localStorage.setItem('fd_expanded_folders', JSON.stringify(data.expandedFolders));
+        if (data.sectionsOpen) localStorage.setItem('fd_sections', JSON.stringify(data.sectionsOpen));
+      }
+    } catch(e) {}
+  });
 </script>
 <script src="/static/js/app.js" defer></script>
 {% block scripts %}{% endblock %}