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/plugins/api_client.js

@@ -212,8 +212,16 @@ const PluginAPI = {
         // Use throttling for GET requests, immediate execution for POST/PUT/DELETE
         if (useThrottle && method === 'GET') {
             return await RequestThrottler.throttle(requestKey, makeRequest, 100);
-        } else {
+        } else if (method === 'GET') {
             return await makeRequest();
+        } else {
+            // A write (install, uninstall, toggle, config save) can change any
+            // cached GET, e.g. the installed list; drop the cache once it lands.
+            try {
+                return await makeRequest();
+            } finally {
+                RequestThrottler.clearCache();
+            }
         }
     },