Add External Services plugin settings section

Expose plugins that declare the external settings section from the External Services settings page.

Wire the sidebar item, subsection mount, and settings DOX contract so plugin sections use matching tab IDs.

webui/components/settings/AGENTS.md

@@ -14,6 +14,7 @@
 ## Local Contracts
 
 - Keep settings payloads synchronized with backend APIs and plugin settings contracts.
+- Settings tabs that expose plugin `settings_sections` must mount `settings/plugins/plugins-subsection.html` with matching `data-tab` and sidebar/nav section IDs.
 - Do not store secrets in localStorage, URLs, or console output.
 - Preserve Store Gating and modal footer conventions in settings components.
 - MCP manager tool toggles write `disabled_tools` into the draft JSON and require Apply before changing the running MCP tool set.

webui/components/settings/external/external-settings.html

@@ -45,6 +45,12 @@
                   <span>Remote Control</span>
                 </a>
               </li>
+              <li>
+                <a href="#section-external-plugins">
+                  <span class="material-symbols-outlined" aria-hidden="true">extension</span>
+                  <span>Plugins</span>
+                </a>
+              </li>
             </ul>
           </nav>
 
@@ -67,6 +73,9 @@
           <div id="section-tunnel" class="section">
             <x-component path="settings/tunnel/tunnel-section.html"></x-component>
           </div>
+          <div id="section-external-plugins" class="section">
+            <x-component path="settings/plugins/plugins-subsection.html" data-tab="external"></x-component>
+          </div>
         </div>
       </template>
     </div>

webui/components/settings/settings-store.js

@@ -49,6 +49,7 @@ const TAB_ITEMS = Object.freeze([
       { id: "section-auth", label: "Authentication", icon: "passkey" },
       { id: "section-external-api", label: "External API", icon: "api" },
       { id: "section-tunnel", label: "Remote Control", icon: "share" },
+      { id: "section-external-plugins", label: "Plugins", icon: "extension" },
     ],
   },
   {