agent: Change the navigation menu keybinding (#31709)

As much as I enjoyed the previous keybinding, it was causing a conflict
with the editor where it wouldn't open on text threads. To not get into
a rabbit hole and complicate the fix too much, I figured simply changing
it to something non-conflictual would be a good move.

Release Notes:

- agent: Fixed a bug where the panel navigation menu wouldn't open with
the keybinding on text threads.

assets/keymaps/default-linux.json

@@ -244,7 +244,7 @@
       "ctrl-i": "agent::ToggleProfileSelector",
       "ctrl-alt-/": "agent::ToggleModelSelector",
       "ctrl-shift-a": "agent::ToggleContextPicker",
-      "ctrl-shift-o": "agent::ToggleNavigationMenu",
+      "ctrl-shift-j": "agent::ToggleNavigationMenu",
       "ctrl-shift-i": "agent::ToggleOptionsMenu",
       "shift-alt-escape": "agent::ExpandMessageEditor",
       "ctrl-alt-e": "agent::RemoveAllContext",

assets/keymaps/default-macos.json

@@ -279,7 +279,7 @@
       "cmd-i": "agent::ToggleProfileSelector",
       "cmd-alt-/": "agent::ToggleModelSelector",
       "cmd-shift-a": "agent::ToggleContextPicker",
-      "cmd-shift-o": "agent::ToggleNavigationMenu",
+      "cmd-shift-j": "agent::ToggleNavigationMenu",
       "cmd-shift-i": "agent::ToggleOptionsMenu",
       "shift-alt-escape": "agent::ExpandMessageEditor",
       "cmd-alt-e": "agent::RemoveAllContext",