feat(ai): neo-configurations for gptel

I misunderstand gptel for a long time. It's powerful and flexible, allow me to
ask LLM in any buffer and write in org-mode style, even persist chatting
sessions in text files. With customized directives and system messages, I can
make LLM play different roles - that's amazing!

lisp/init-ai.el

@@ -2,23 +2,50 @@
 ;;; Commentary:
 ;;; Code:
 
+
+;;; gptel
 (use-package gptel
   :init
-  (celeste/prepare-package transient)
-  (celeste/prepare-package compat)
-  (celeste/prepare-package gptel)
-  :commands (gptel
-             gptel-send)
+  (celeste/prepare-package (transient compat markdown-mode))
+  (celeste/package-autoload 'gptel)
+  (with-eval-after-load 'embark
+    (defvar-keymap embark-gptel-map
+      :doc "Keymap for gptel."
+      :parent nil
+      "a" #'gptel-add
+      "m" #'gptel-menu
+      "s" #'gptel-send)
+    (fset 'embark-gptel-map embark-gptel-map)
+    (keymap-set embark-region-map "g" #'embark-gptel-map))
   :config
-  ;; `gptel-curl-get-response'
-  (require 'gptel-curl)
-  ;; `gptel-system-prompt'
-  (require 'gptel-transient)
+  (setq gptel-display-buffer-action nil)
+  (setq gptel-default-mode 'org-mode)
+  (add-hook 'gptel-mode-hook
+            (defun +gptel-mode-override-settings ()
+              (when (fboundp 'whitespace-display-mode)
+                (whitespace-display-mode -1))
+              (auto-fill-mode -1)
+              (visual-line-mode +1)))
+
+  ;; Customize prompt/response prefixes. These prefixes will be trimmed to form
+  ;; the final request body, check `gptel--parse-buffer'.
+  (setq gptel-prompt-prefix-alist
+        '((markdown-mode . "**Prompt**: ")
+          (org-mode . "*Prompt*: ")
+          (text-mode . "### ")))
+  (setq gptel-response-prefix-alist
+        '((markdown-mode . "**Response**:\n")
+          (org-mode . "*Response*:\n")
+          (text-mode . "")))
+
+  ;; This is necessary for using `gptel-menu' in Vterm buffer.
+  (with-eval-after-load 'vterm
+    (keymap-unset vterm-copy-mode-map "<return>" t))
 
-  (setq gptel-display-buffer-action (list #'display-buffer-same-window))
   )
 
 
+
 (provide 'init-ai)
 ;;; init-ai.el ends here