fix(mu4e): cursor to body after headers on message open

Modern mu4e (1.8+) uses gnus-article-mode, not mu4e-view-mode,
so mu4e-view-mode-hook never fired. Fix:
- Use gnus-article-prepare-hook (primary) + mu4e-view-mode-hook (fallback)
- Target *mu4e-article* buffer explicitly via when-let
- Skip header lines by pattern (Key: value / continuation) instead of blank line
- Add idle timer (0.05s) to ensure buffer is fully populated

config.el

@@ -657,11 +657,27 @@ and optional priority indicator [#A]."
   (setq message-cite-function #'message-cite-original-without-signature)
 
   ;; Move cursor past headers to message body when opening a message
+  ;; Modern mu4e (1.8+) uses gnus-article-mode, not mu4e-view-mode.
+  ;; We use mu4e-view-rendered-hook which fires after the message is displayed,
+  ;; with a small idle timer to ensure the buffer is fully populated.
   (defun my/mu4e-view-goto-body ()
     "Position cursor at the start of the message body, skipping headers."
-    (goto-char (point-min))
-    (when (re-search-forward "^$" nil t)
-      (forward-line 1)))
+    (run-with-idle-timer
+     0.05 nil
+     (lambda ()
+       (when-let ((buf (get-buffer "*mu4e-article*")))
+         (with-current-buffer buf
+           (goto-char (point-min))
+           ;; Skip header block: lines matching "Key: value" or continuation whitespace
+           (while (and (not (eobp))
+                       (looking-at "^\\([A-Za-z-]+:\\|[ \t]\\)"))
+             (forward-line 1))
+           ;; Skip blank separator line(s)
+           (while (and (not (eobp)) (looking-at "^\\s-*$"))
+             (forward-line 1)))))))
+  ;; Hook into gnus-article-prepare-hook (fires in gnus-based mu4e view)
+  (add-hook 'gnus-article-prepare-hook #'my/mu4e-view-goto-body)
+  ;; Also keep mu4e-view-mode-hook as fallback for older mu4e / non-gnus view
   (add-hook 'mu4e-view-mode-hook #'my/mu4e-view-goto-body)
   ;; Maildir shortcuts
   (setq mu4e-maildir-shortcuts