feat: RHS panel + channel header button + public icon

- Switched from registerAppBarComponent (not in MM 11.4 build) to
  registerChannelHeaderButtonAction + registerRightHandSidebarComponent
- Added public/icon.svg for channel header button
- Fixed store dispatch for RHS toggle action
- Plugin deployment permissions fix (uid 2000)

plugin/server/public/icon.svg

@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="#166de0">
+  <path d="M20 4H4c-1.1 0-2 .9-2 2v12c0 1.1.9 2 2 2h16c1.1 0 2-.9 2-2V6c0-1.1-.9-2-2-2zm-1 14H5V6h14v12zM7 9h2v2H7zm0 4h2v2H7zm4-4h6v2h-6zm0 4h6v2h-6z"/>
+</svg>

plugin/webapp/src/index.tsx

@@ -1,3 +1,4 @@
+import React from 'react';
 import { PluginRegistry, WebSocketPayload, LiveStatusData } from './types';
 import LiveStatusPost from './components/live_status_post';
 import RHSPanel from './components/rhs_panel';
@@ -16,13 +17,24 @@ class LiveStatusPlugin {
       LiveStatusPost,
     );
 
-    // Register RHS panel with AppBar icon
-    // This creates both the sidebar component and the toolbar button to toggle it
-    registry.registerAppBarComponent({
-      iconUrl: '', // Empty = use default plugin icon from assets/icon.svg
-      tooltipText: 'Agent Status',
-      rhsComponent: RHSPanel,
-      rhsTitle: 'Agent Status',
+    // Register RHS sidebar component
+    const rhsResult = registry.registerRightHandSidebarComponent({
+      component: RHSPanel,
+      title: 'Agent Status',
+    });
+
+    // Add channel header button to toggle the RHS panel
+    const toggleAction = rhsResult.toggleRHSPlugin;
+    registry.registerChannelHeaderButtonAction({
+      icon: React.createElement('i', {
+        className: 'icon icon-cog-outline',
+        style: { fontSize: '18px' },
+      }),
+      action: () => {
+        store.dispatch(toggleAction);
+      },
+      dropdownText: 'Agent Status',
+      tooltipText: 'Toggle Agent Status panel',
     });
 
     // Register WebSocket event handler