feat: add collapsible Beam inspector

frontend/index.html

@@ -124,9 +124,18 @@
       </div>
     </section>
 
-    <aside class="side-panel">
+    <aside class="side-panel" id="viewerInspector">
       <div class="panel-section">
-        <h3>Инспектор</h3>
+        <div class="inspector-panel-header">
+          <h3>Инспектор</h3>
+          <button
+            class="inspector-collapse-btn"
+            id="inspectorCollapseButton"
+            type="button"
+            title="Свернуть инспектор"
+            aria-label="Свернуть инспектор"
+          >▁</button>
+        </div>
         <div id="treeContainer" class="tree"></div>
         <div class="inspector-controls">
           <div class="inspector-control-row inspector-control-row--half" id="displayModeControl">
@@ -190,6 +199,9 @@
         <button class="secondary-btn danger-btn" id="deleteProjectButton" type="button">Удалить проект</button>
       </div>
     </aside>
+    <div class="inspector-restore-tray" id="inspectorRestoreTray" hidden>
+      <button class="inspector-restore-button" id="inspectorRestoreButton" type="button">Инспектор</button>
+    </div>
   </main>
 
   <div id="templatesPanel" class="templates-panel hidden"></div>