Replace Nebot plugin with Return YouTube Dislike

Removed the Nebot chat plugin and its files, and added the Return YouTube Dislike plugin with main process logic, renderer preload, and manifest. Updated plugin manager and main process to support internal plugin pages and improved plugin event handling. Minor updates to renderer and documentation.

main.js

@@ -787,6 +787,11 @@ ipcMain.handle('plugins-get-renderer-preloads', () => {
   try { return pluginManager.getRendererPreloads(); } catch { return []; }
 });
 
+// Plugins: expose registered internal pages (browser://<id>)
+ipcMain.handle('plugins-get-pages', () => {
+  try { return pluginManager.getRendererPages(); } catch { return []; }
+});
+
 // Plugins: management IPC for settings UI
 ipcMain.handle('plugins-list', () => pluginManager.discoverPlugins());
 ipcMain.handle('plugins-set-enabled', async (_e, { id, enabled }) => {
@@ -806,6 +811,9 @@ app.on('web-contents-created', (event, contents) => {
     buildAndShowContextMenu(contents, params);
   });
 
+  // Emit to plugins
+  try { pluginManager.emit('web-contents-created', contents); } catch {}
+
   // On macOS, when a page (or a <webview>) enters HTML fullscreen (e.g., YouTube video),
   // also toggle the BrowserWindow into simple fullscreen so the content uses the whole
   // screen and macOS traffic lights/titlebar are hidden. Revert when HTML fullscreen exits.