refactor + add some QoL plugins

config/plugins/cmp/copilot-chat.nix

@@ -0,0 +1,65 @@
+{ ... }: {
+  plugins.copilot-chat = {
+    enable = true;
+
+    # Copilot Chat settings.
+    settings = {
+      # Model to use for Copilot Chat.
+      model = "gpt-4.1";
+      # Use all buffers for context.
+      context = "buffers";
+      # Use yanked text for selection.
+      selection = "unnamed";
+      # Don't highlight the selection.
+      highlight_selection = false;
+      # Window settings for Copilot Chat.
+      window = {
+        # Width of the chat window.
+        width = 0.3;
+      };
+    };
+  };
+
+  # Keymaps for Copilot Chat.
+  keymaps = [
+    {
+      mode = ["n" "v"];
+      key = "<leader>ct";
+      action = "<cmd>CopilotChatToggle<cr>";
+      options = {
+        silent = true;
+        desc = "Toggle chat";
+      };
+    }
+
+    {
+      mode = ["n" "v"];
+      key = "<leader>cp";
+      action = "<cmd>CopilotChatPrompts<cr>";
+      options = {
+        silent = true;
+        desc = "Select prompt";
+      };
+    }
+
+    {
+      mode = ["n"];
+      key = "<leader>cm";
+      action = "<cmd>CopilotChatModels<cr>";
+      options = {
+        silent = true;
+        desc = "Select model";
+      };
+    }
+
+    {
+      mode = ["n"];
+      key = "<leader>ca";
+      action = "<cmd>CopilotChatAgents<cr>";
+      options = {
+        silent = true;
+        desc = "Select agent";
+      };
+    }
+  ];
+}