feat(ai): send quick explanation to *gptel* buffer instead of message

ai.el

@@ -156,14 +156,28 @@
 ;;; ============================================================================
 
 (defun my/gptel-quick-explain-region ()
-  "Quickly explain selected code region."
+  "Quickly explain selected code region in the gptel buffer."
   (interactive)
   (when (use-region-p)
-    (let ((code (buffer-substring-no-properties (region-beginning) (region-end))))
-      (gptel-request code
-        :system "Explain this code concisely in 2-3 sentences."
+    (let* ((code (buffer-substring-no-properties (region-beginning) (region-end)))
+           (buf (get-buffer-create "*gptel*")))
+      ;; Prepare the buffer and insert the query immediately
+      (with-current-buffer buf
+        (goto-char (point-max))
+        (unless (derived-mode-p 'gptel-mode)
+          (funcall gptel-default-mode)
+          (gptel-mode 1))
+        (insert "\n\n--- Code to Explain ---\n\n" code "\n\n### Explanation Request Sent...\n"))
+      (display-buffer buf)
+      ;; Send the request
+      (gptel-request
+          (format "Explain this code concisely in 2-3 sentences:\n\n%s" code)
+        :system "You are an expert programmer explaining code."
         :callback (lambda (response info)
-                    (message "Explanation: %s" response))))))
+                    (with-current-buffer (get-buffer "*gptel*")
+                      (goto-char (point-max))
+                      (insert "\n### Code Explanation\n\n" response "\n\n"))
+                    (message "Explanation received in *gptel* buffer."))))))
 
 (defun my/gptel-proofread-region ()
   "Proofread and improve selected text."