refactor: move DSA notes to org/study_deck_02/

Restructure NeetCode study materials into a dedicated Anki-exportable
deck directory. Separates DSA problem notes from C++ flashcards.

- Move roadmap.org from leetcode/out/ to org/study_deck_02/
- Move 200 note files from org/cpp/dsa/ to org/study_deck_02/dsa/
- Add #+PROPERTY: STUDY_DECK_02 to all org files for org-anki export
- Simplify roadmap format: properties drawer replaces nested headings
- Update NEETCODE backlinks in all note files
- Update extract.mjs and scaffold-notes.mjs for new paths
- Create org/study_deck_02/AGENTS.md with study workflow docs
- Update root and leetcode AGENTS.md

org/study_deck_02/dsa/backtracking/0017-letter-combinations-of-a-phone-number.org

@@ -0,0 +1,18 @@
+* TODO 0017. Letter Combinations of a Phone Number :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0017. Letter Combinations of a Phone Number][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0022-generate-parentheses.org

@@ -0,0 +1,18 @@
+* TODO 0022. Generate Parentheses :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0022. Generate Parentheses][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0039-combination-sum.org

@@ -0,0 +1,18 @@
+* TODO 0039. Combination Sum :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0039. Combination Sum][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0040-combination-sum-ii.org

@@ -0,0 +1,18 @@
+* TODO 0040. Combination Sum II :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0040. Combination Sum II][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0046-permutations.org

@@ -0,0 +1,18 @@
+* TODO 0046. Permutations :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0046. Permutations][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0051-n-queens.org

@@ -0,0 +1,18 @@
+* TODO 0051. N Queens :hard:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0051. N Queens][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0052-n-queens-ii.org

@@ -0,0 +1,18 @@
+* TODO 0052. N Queens II :hard:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0052. N Queens II][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0077-combinations.org

@@ -0,0 +1,18 @@
+* TODO 0077. Combinations :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0077. Combinations][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0078-subsets.org

@@ -0,0 +1,18 @@
+* TODO 0078. Subsets :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0078. Subsets][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0079-word-search.org

@@ -0,0 +1,18 @@
+* TODO 0079. Word Search :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0079. Word Search][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0090-subsets-ii.org

@@ -0,0 +1,18 @@
+* TODO 0090. Subsets II :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0090. Subsets II][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0131-palindrome-partitioning.org

@@ -0,0 +1,18 @@
+* TODO 0131. Palindrome Partitioning :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0131. Palindrome Partitioning][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/0351-android-unlock-patterns.org

@@ -0,0 +1,18 @@
+* TODO 0351. Android Unlock Patterns :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0351. Android Unlock Patterns][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/1079-letter-tile-possibilities.org

@@ -0,0 +1,18 @@
+* TODO 1079. Letter Tile Possibilities :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*1079. Letter Tile Possibilities][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src

org/study_deck_02/dsa/backtracking/1863-sum-of-all-subsets-xor-total.org

@@ -0,0 +1,18 @@
+* TODO 1863. Sum of All Subsets XOR Total :easy:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*1863. Sum of All Subsets XOR Total][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src