fix(update): separate in-flight dedup keys for manual check vs install

- manual:check and manual:install now tracked independently; install no longer reuses a check's in-flight promise
- add toggleNotificationHistory (Ctrl+N) shortcut to config example and docs

docs-site/public/config.example.jsonc

@@ -208,7 +208,8 @@
     "openSessionHelp": "CommandOrControl+Slash", // Accelerator that opens the session help / keybinding cheatsheet.
     "openControllerSelect": "Alt+C", // Accelerator that opens the controller selection and learn-mode modal.
     "openControllerDebug": "Alt+Shift+C", // Accelerator that opens the controller debug modal with live axis/button readouts.
-    "toggleSubtitleSidebar": "Backslash" // Accelerator that toggles the subtitle sidebar visibility.
+    "toggleSubtitleSidebar": "Backslash", // Accelerator that toggles the subtitle sidebar visibility.
+    "toggleNotificationHistory": "Ctrl+N" // Accelerator that toggles the overlay notification history panel.
   }, // Overlay keyboard shortcuts. Set a shortcut to null to disable.
 
   // ==========================================

docs-site/shortcuts.md

@@ -82,6 +82,7 @@ Mouse-hover playback behavior is configured separately from shortcuts: `subtitle
 | `Ctrl/Cmd+Shift+O` | Open runtime options palette                             | `shortcuts.openRuntimeOptions`                  |
 | `Ctrl/Cmd+/`       | Open session help modal                                  | `shortcuts.openSessionHelp`                     |
 | `Ctrl+Shift+J`     | Open Jimaku subtitle search modal                        | `shortcuts.openJimaku`                          |
+| `Ctrl+N`           | Toggle overlay notification history panel                | `shortcuts.toggleNotificationHistory`           |
 | `Ctrl+Alt+C`       | Open the manual YouTube subtitle picker                  | `keybindings`                                   |
 | `Ctrl+Alt+S`       | Open subtitle sync (subsync) modal                       | `shortcuts.triggerSubsync`                      |
 | `\`                | Toggle subtitle sidebar                                  | `subtitleSidebar.toggleKey`                     |