Add solution notes scaffold and sub-heading format

- roadmap.org: problems now have *** Python and *** C++ sub-headings,
  plus Notes: links to per-problem org files
- scaffold-notes.mjs: creates 199 note files in org/cpp/dsa/<topic>/
  with backlinks to roadmap.org
- 18 topic folders under org/cpp/dsa/ for NeetCode 150 problems
- Updated AGENTS.md with new conventions and workflow

org/cpp/dsa/stack/0020-valid-parentheses.org

@@ -0,0 +1,8 @@
+* TODO 0020. Valid Parentheses :easy:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0020. Valid Parentheses][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/0084-largest-rectangle-in-histogram.org

@@ -0,0 +1,8 @@
+* TODO 0084. Largest Rectangle In Histogram :hard:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0084. Largest Rectangle In Histogram][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/0150-evaluate-reverse-polish-notation.org

@@ -0,0 +1,8 @@
+* TODO 0150. Evaluate Reverse Polish Notation :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0150. Evaluate Reverse Polish Notation][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/0155-min-stack.org

@@ -0,0 +1,8 @@
+* TODO 0155. Min Stack :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0155. Min Stack][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/0682-baseball-game.org

@@ -0,0 +1,8 @@
+* TODO 0682. Baseball Game :easy:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0682. Baseball Game][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/0726-number-of-atoms.org

@@ -0,0 +1,8 @@
+* TODO 0726. Number of Atoms :hard:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0726. Number of Atoms][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/0739-daily-temperatures.org

@@ -0,0 +1,8 @@
+* TODO 0739. Daily Temperatures :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0739. Daily Temperatures][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/0853-car-fleet.org

@@ -0,0 +1,8 @@
+* TODO 0853. Car Fleet :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0853. Car Fleet][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/0901-online-stock-span.org

@@ -0,0 +1,8 @@
+* TODO 0901. Online Stock Span :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0901. Online Stock Span][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/stack/1544-make-the-string-great.org

@@ -0,0 +1,8 @@
+* TODO 1544. Make The String Great :easy:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*1544. Make The String Great][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src