feat: REPLs, by major mode, by project

Also includes Doom's popup code. }:)

users/crumb/programs/emacs/lib/syd-prelude.el

@@ -7,7 +7,7 @@
 (cl-defmacro syd-define-stub
     (name &key (desc "implement me!") interactive)
   (let ((todo (format "%s: TODO: %s" name desc)))
-    `(defun ,name (&rest args)
+    `(defun ,name (&rest _)
        ,@(if interactive (list '(interactive)) nil)
        ,todo
        (error ,todo))))