refactor(config): Update Emacs configuration across multiple modules

- Prefix gptel backend names with "gptel-" for consistency
- Add denote-org-backlinks-for-heading keybinding
- Refine recentf exclusions for org journal files
- Remove org-default-priority setting
- Add gptel and denote backlink buffer rules to ibuffer
- Enable markdown-ts-mode for Emacs 31+ with truncate lines
- Add electric-pair support for equals sign
- Update popper and window management regexes for new buffer names

lisp/init-prog.el

@@ -35,14 +35,17 @@
 
 ;; markdown
 (use-package markdown-mode
-  :mode
-  ("README\\.md\\'" . gfm-mode)
-  :init
-  (setq markdown-command "multimarkdown")
   :bind
   (:map markdown-mode-map
-              ("C-c C-e" . markdown-do)))
-
+        ("C-c C-e" . markdown-do))
+  :hook
+  (markdown-mode . toggle-truncate-lines)
+  :init
+  (setq markdown-command "multimarkdown")
+  (when (>= emacs-major-version 31)
+    (add-to-list 'major-mode-remap-alist
+		 '(markdown-mode . markdown-ts-mode))
+    (add-hook 'markdown-ts-mode-hook #'toggle-truncate-lines)))
 
 (provide 'init-prog)