feat(sidebar): Notion-style collapse/peek, desktop reopen button, Ctrl+\\ toggle

Stop collapsing the sidebar on navigation (was hiding the nav when opening Shared pages). Show the hamburger in the top-left on desktop when collapsed, add a left-edge hover zone that floats the sidebar in and auto-collapses on mouse leave, and bind Ctrl/Cmd+\\ to toggle it.

app/templates/_header.html

@@ -36,7 +36,8 @@
 <header class="topbar unified-header">
   {% if not hide_hamburger %}
   <button class="hamburger-btn"
-          @click="{{ hamburger_click|default('sidebarCollapsed ? (sidebarCollapsed = false) : (mobileSidebarOpen = true, sidebarCollapsed = false)') }}"
+          :class="{ 'hamburger-desktop-show': sidebarCollapsed }"
+          @click="{{ hamburger_click|default('sidebarCollapsed ? toggleSidebar() : (mobileSidebarOpen = true, sidebarCollapsed = false)') }}"
           title="Toggle sidebar">
     <svg width="22" height="22" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
       <line x1="3" y1="6" x2="21" y2="6"/>

app/templates/base.html

@@ -5,7 +5,7 @@
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>FlowDeck — {% block title_prefix %}Home{% endblock %}</title>
   <link rel="icon" type="image/svg+xml" href="/static/favicon.svg">
-  <link rel="stylesheet" href="/static/css/app.css?v=5.0.0">
+  <link rel="stylesheet" href="/static/css/app.css?v=5.0.1">
   <link rel="stylesheet" href="/static/css/design-tokens.css?v=5.2.0">
   <link rel="stylesheet" href="/static/css/components.css?v=5.2.0">
   <link rel="stylesheet" href="/static/css/katex.min.css?v=0.16.11">
@@ -118,9 +118,14 @@
   <!-- ═══════════ MOBILE SIDEBAR OVERLAY ═══════════ -->
   <div class="sidebar-overlay"
        :class="{ visible: mobileSidebarOpen }"
-       @click="mobileSidebarOpen = false, sidebarCollapsed = true">
+       @click="mobileSidebarOpen = false">
   </div>
 
+  <!-- ═══════════ SIDEBAR PEEK ZONE (collapsed, desktop) ═══════════ -->
+  <div class="sidebar-peek-zone"
+       x-show="sidebarCollapsed" x-cloak
+       @mouseenter="sidebarPeek = true"></div>
+
 {# ─── Recursive tree macro ─── #}
 {% macro render_tree_item(page, depth=0) %}
   {% set indent_px = depth * 16 %}
@@ -163,8 +168,9 @@
 
   <!-- ═══════════ SIDEBAR Notion ═══════════ -->
   <aside class="sidebar"
-         :class="{ collapsed: sidebarCollapsed, 'mobile-open': mobileSidebarOpen }"
+         :class="{ collapsed: sidebarCollapsed && !sidebarPeek, 'mobile-open': mobileSidebarOpen, peeking: sidebarPeek }"
          id="sidebar"
+         @mouseleave="sidebarPeek = false"
          x-init="$nextTick(() => { if(typeof initTreeSortable==='function') initTreeSortable(); })">
     <!-- Header + dropdown wrapper -->
     <div style="position:relative;">
@@ -180,7 +186,7 @@
         {% endif %}
       </div>
       <span class="workspace-chevron" :class="{ open: workspaceMenuOpen }">▾</span>
-      <button class="sidebar-collapse-inline" @click.stop="sidebarCollapsed = !sidebarCollapsed" title="Collapse sidebar">
+      <button class="sidebar-collapse-inline" @click.stop="toggleSidebar()" title="Collapse sidebar">
         <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polyline points="11 17 6 12 11 7"/><polyline points="18 17 13 12 18 7"/></svg>
       </button>
     </div>
@@ -963,6 +969,7 @@
         window.appState = this;
         this.loadSidebarConfig();
         this.loadAgents();
+        document.addEventListener('fd-toggle-sidebar', () => this.toggleSidebar());
       },
       agentList: [],
       loadAgents() {
@@ -980,6 +987,7 @@
         else { document.dispatchEvent(new CustomEvent('fd-agent-toggle')); }
       },
       sidebarCollapsed: false,
+      sidebarPeek: false,
       mobileSidebarOpen: false,
       showInvite: true,
       // -- Toast notifications --
@@ -1325,7 +1333,7 @@
 
       navigateTo(url) {
         this.mobileSidebarOpen = false;
-        this.sidebarCollapsed = true;
+        this.sidebarPeek = false;
         // Preserve workspace context when navigating to library/trash
         if ((url === '/library' || url === '/trash') && this.workspaceKey && this.workspaceKey.includes('/')) {
           const parts = this.workspaceKey.split('/');
@@ -1335,6 +1343,11 @@
         else window.location.href = url;
       },
 
+      toggleSidebar() {
+        this.sidebarPeek = false;
+        this.sidebarCollapsed = !this.sidebarCollapsed;
+      },
+
       showContextMenu(event, pageId, pageName) {
         var x = event.clientX, y = event.clientY;
         // Prevent menu from overflowing right edge
@@ -1842,7 +1855,7 @@
     }
   });
 </script>
-<script src="/static/js/app.js?v=2.4.7" defer></script>
+<script src="/static/js/app.js?v=2.4.8" defer></script>
 
 <style>
 .flowdeck-modal-overlay{position:fixed;top:0;left:0;right:0;bottom:0;background:rgba(0,0,0,0.6);z-index:2000;display:flex;align-items:center;justify-content:center;}