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/two-pointers/0011-container-with-most-water.org

@@ -0,0 +1,8 @@
+* TODO 0011. Container With Most Water :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0011. Container With Most Water][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/two-pointers/0015-3sum.org

@@ -0,0 +1,8 @@
+* TODO 0015. 3Sum :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0015. 3Sum][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/two-pointers/0042-trapping-rain-water.org

@@ -0,0 +1,8 @@
+* TODO 0042. Trapping Rain Water :hard:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0042. Trapping Rain Water][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/two-pointers/0125-valid-palindrome.org

@@ -0,0 +1,8 @@
+* TODO 0125. Valid Palindrome :easy:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0125. Valid Palindrome][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/two-pointers/0167-two-sum-ii-input-array-is-sorted.org

@@ -0,0 +1,8 @@
+* TODO 0167. Two Sum II Input Array Is Sorted :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0167. Two Sum II Input Array Is Sorted][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/two-pointers/0259-3sum-smaller.org

@@ -0,0 +1,8 @@
+* TODO 0259. 3Sum Smaller :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0259. 3Sum Smaller][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/two-pointers/0344-reverse-string.org

@@ -0,0 +1,8 @@
+* TODO 0344. Reverse String :easy:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0344. Reverse String][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src