fix: add file: prefix to org-mode links for Emacs resolution

Emorg org-mode requires [[file:path]] syntax for file links to be
clickable. Updated both extract.mjs and scaffold-notes.mjs generators,
and fixed all 200 existing note files.

leetcode/AGENTS.md

@@ -83,7 +83,7 @@ Scaffolded by `scaffold-notes.mjs`. Template:
 * TODO 0217. Contains Duplicate :easy:
 #+PROPERTY: STUDY_DECK_02
 :PROPERTIES:
-:NEETCODE: [[../../roadmap.org::*0217. Contains Duplicate][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0217. Contains Duplicate][Roadmap]]
 :END:
 
 #+begin_src cpp