agent: Support vim-mode in the agent panel's editor (#31915)

Closes #30081

Release Notes:

- Added vim-mode support in the agent panel's editor

---------

Co-authored-by: Ben Kunkle <ben.kunkle@gmail.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

assets/keymaps/vim.json

@@ -838,6 +838,19 @@
       "tab": "editor::AcceptEditPrediction"
     }
   },
+  {
+    "context": "MessageEditor > Editor && VimControl",
+    "bindings": {
+      "enter": "agent::Chat",
+      // TODO: Implement search
+      "/": null,
+      "?": null,
+      "#": null,
+      "*": null,
+      "n": null,
+      "shift-n": null
+    }
+  },
   {
     "context": "os != macos && Editor && edit_prediction_conflict",
     "bindings": {