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/backtracking/0017-letter-combinations-of-a-phone-number.org

@@ -0,0 +1,8 @@
+* TODO 0017. Letter Combinations of a Phone Number :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0017. Letter Combinations of a Phone Number][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0022-generate-parentheses.org

@@ -0,0 +1,8 @@
+* TODO 0022. Generate Parentheses :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0022. Generate Parentheses][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0039-combination-sum.org

@@ -0,0 +1,8 @@
+* TODO 0039. Combination Sum :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0039. Combination Sum][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0040-combination-sum-ii.org

@@ -0,0 +1,8 @@
+* TODO 0040. Combination Sum II :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0040. Combination Sum II][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0046-permutations.org

@@ -0,0 +1,8 @@
+* TODO 0046. Permutations :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0046. Permutations][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0051-n-queens.org

@@ -0,0 +1,8 @@
+* TODO 0051. N Queens :hard:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0051. N Queens][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0052-n-queens-ii.org

@@ -0,0 +1,8 @@
+* TODO 0052. N Queens II :hard:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0052. N Queens II][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0077-combinations.org

@@ -0,0 +1,8 @@
+* TODO 0077. Combinations :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0077. Combinations][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0078-subsets.org

@@ -0,0 +1,8 @@
+* TODO 0078. Subsets :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0078. Subsets][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0079-word-search.org

@@ -0,0 +1,8 @@
+* TODO 0079. Word Search :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0079. Word Search][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0090-subsets-ii.org

@@ -0,0 +1,8 @@
+* TODO 0090. Subsets II :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0090. Subsets II][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0131-palindrome-partitioning.org

@@ -0,0 +1,8 @@
+* TODO 0131. Palindrome Partitioning :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0131. Palindrome Partitioning][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/0351-android-unlock-patterns.org

@@ -0,0 +1,8 @@
+* TODO 0351. Android Unlock Patterns :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0351. Android Unlock Patterns][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/1079-letter-tile-possibilities.org

@@ -0,0 +1,8 @@
+* TODO 1079. Letter Tile Possibilities :medium:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*1079. Letter Tile Possibilities][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src

org/cpp/dsa/backtracking/1863-sum-of-all-subsets-xor-total.org

@@ -0,0 +1,8 @@
+* TODO 1863. Sum of All Subsets XOR Total :easy:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*1863. Sum of All Subsets XOR Total][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src