fix(menus): observe sidePanel.open promise to avoid unhandled rejections

The synchronous menuConfig.openSidePanel.action(true, tab) call is
intentional — chrome.sidePanel.open() must run inside the user-gesture
callback or it throws 'sidePanel.open() may only be called in response
to a user gesture'. We don't want to break that.

But the action used to be async, so the chrome.sidePanel.open Promise
was discarded and any rejection (e.g. an invalid tab/window combo)
would surface as an unhandled rejection in the background script.

Two small changes:
- menu-tools/index.mjs: drop the async wrapper and return the
  chrome.sidePanel.open() promise directly so the caller can observe it.
- background/menus.mjs: still call the action synchronously (gesture
  preserved) but, if it returned a thenable, attach a .catch that logs
  the failure instead of letting it become unhandled.

Addresses review feedback from CodeRabbit and gemini-code-assist.

Author: octo-patch

src/background/menus.mjs

@@ -12,7 +12,15 @@ const onClickMenu = (info, tab) => {
   // Chrome's user gesture requirement and causes the error:
   // "sidePanel.open() may only be called in response to a user gesture."
   if (itemId === 'openSidePanel' && menuConfig.openSidePanel?.action) {
-    menuConfig.openSidePanel.action(true, tab)
+    // Keep the call synchronous to preserve the user-gesture requirement,
+    // but observe the returned Promise so a rejected sidePanel.open() does
+    // not become an unhandled rejection in the background script.
+    const result = menuConfig.openSidePanel.action(true, tab)
+    if (result && typeof result.catch === 'function') {
+      result.catch((error) => {
+        console.error('failed to open side panel', error)
+      })
+    }
     return
   }
 

src/content-script/menu-tools/index.mjs

@@ -59,14 +59,14 @@ export const config = {
   },
   openSidePanel: {
     label: 'Open Side Panel',
-    action: async (fromBackground, tab) => {
+    action: (fromBackground, tab) => {
       console.debug('action is from background', fromBackground)
       if (fromBackground) {
         // eslint-disable-next-line no-undef
-        chrome.sidePanel.open({ windowId: tab.windowId, tabId: tab.id })
-      } else {
-        // side panel is not supported
+        return chrome.sidePanel.open({ windowId: tab.windowId, tabId: tab.id })
       }
+      // side panel is not supported
+      return undefined
     },
   },
   closeAllChats: {