fix(web): seven web UI bugs, and remove dead plugins_manager.js helpers (#647)

- Operation History: the plugin filter lists the installed plugin ids
  instead of one option, "plugins" (Object.keys of {plugins: [...]}).
- Ctrl/Cmd+S submits the active tab's first visible form with
  requestSubmit() (validation and onsubmit guards run) instead of a bare
  Event on the first form in the document; skipped inside a modal dialog
  and on tabs without a form.
- Overview "Check Updates" confirms like "Update Code", takes its button
  explicitly (no implicit global event) and shows the server's message.
  Both, and the Tools tab git pull, raise the restart-pending banner on
  restart_required.
- Tools: toolsAction and diagnostics show the server's error message;
  only a non-JSON body falls back to HTTP <status>.
- Installed list after uninstall: PluginAPI writes clear the throttler's
  GET cache, a forced loadInstalledPlugins clears it too, and the
  post-uninstall reload goes through refreshInstalledPlugins().
- Plugin widgets load from /static/plugin-widgets/ only (the other two
  paths have no route).
- Raw JSON editor escapes the parse error; slider escapes value/min/max/step.
- Removed the unreferenced array-of-objects and key-value helpers from
  plugins_manager.js, the textarea auto-resize and Ctrl+R handlers in
  app.js, and a redundant ?v= on the plugins_manager.js script tag.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

web_interface/static/v3/js/widgets/plugin-loader.js

@@ -33,11 +33,11 @@
             return;
         }
 
-        // Try multiple possible paths for plugin widgets
+        // The one route that serves plugin widgets (serve_plugin_widget in
+        // blueprints/pages_v3.py); nothing is served under /plugins/<id>/ or
+        // /static/plugins/<id>/, so trying those only added two failed imports.
         const possiblePaths = [
-            `/static/plugin-widgets/${pluginId}/${widgetName}.js`,
-            `/plugins/${pluginId}/widgets/${widgetName}.js`,
-            `/static/plugins/${pluginId}/widgets/${widgetName}.js`
+            `/static/plugin-widgets/${pluginId}/${widgetName}.js`
         ];
 
         let lastError = null;