assistant2: Add Linux keybindings following same pattern as macOS (#22874)

Release Notes:

- N/A

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

assets/keymaps/default-linux.json

@@ -567,6 +567,23 @@
       "alt-enter": "editor::Newline"
     }
   },
+  {
+    "context": "AssistantPanel2",
+    "bindings": {
+      "ctrl-n": "assistant2::NewThread",
+      "ctrl-shift-h": "assistant2::OpenHistory",
+      "ctrl-shift-m": "assistant2::ToggleModelSelector",
+      "ctrl-shift-a": "assistant2::ToggleContextPicker",
+      "ctrl-alt-e": "assistant2::RemoveAllContext"
+    }
+  },
+  {
+    "context": "MessageEditor > Editor",
+    "use_key_equivalents": true,
+    "bindings": {
+      "enter": "assistant2::Chat"
+    }
+  },
   {
     "context": "PromptEditor",
     "bindings": {