agent: Display keybindings for "Reject All" and "Keep All" (#28620)

<img
src="https://github.com/user-attachments/assets/2cdc5121-dd7b-4f46-8d43-88d5152c77ea"
width="550" />


Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -150,7 +150,9 @@
     "context": "AgentDiff",
     "bindings": {
       "ctrl-y": "agent::Keep",
-      "ctrl-n": "agent::Reject"
+      "ctrl-n": "agent::Reject",
+      "ctrl-shift-y": "agent::KeepAll",
+      "ctrl-shift-n": "agent::RejectAll"
     }
   },
   {

assets/keymaps/default-macos.json

@@ -242,7 +242,9 @@
     "use_key_equivalents": true,
     "bindings": {
       "cmd-y": "agent::Keep",
-      "cmd-n": "agent::Reject"
+      "cmd-n": "agent::Reject",
+      "cmd-shift-y": "agent::KeepAll",
+      "cmd-shift-n": "agent::RejectAll"
     }
   },
   {