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/heap-priority-queue/0215-kth-largest-element-in-an-array.org

@@ -0,0 +1,18 @@
+* TODO 0215. Kth Largest Element In An Array :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0215. Kth Largest Element In An Array][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/heap-priority-queue/0295-find-median-from-data-stream.org

@@ -0,0 +1,18 @@
+* TODO 0295. Find Median From Data Stream :hard:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0295. Find Median From Data Stream][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/heap-priority-queue/0355-design-twitter.org

@@ -0,0 +1,18 @@
+* TODO 0355. Design Twitter :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0355. Design Twitter][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/heap-priority-queue/0621-task-scheduler.org

@@ -0,0 +1,18 @@
+* TODO 0621. Task Scheduler :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0621. Task Scheduler][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/heap-priority-queue/0703-kth-largest-element-in-a-stream.org

@@ -0,0 +1,18 @@
+* TODO 0703. Kth Largest Element In a Stream :easy:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0703. Kth Largest Element In a Stream][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/heap-priority-queue/0973-k-closest-points-to-origin.org

@@ -0,0 +1,18 @@
+* TODO 0973. K Closest Points to Origin :medium:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*0973. K Closest Points to Origin][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/heap-priority-queue/1046-last-stone-weight.org

@@ -0,0 +1,18 @@
+* TODO 1046. Last Stone Weight :easy:
+#+PROPERTY: STUDY_DECK_02
+:PROPERTIES:
+:NEETCODE: [[../../roadmap.org::*1046. Last Stone Weight][Roadmap]]
+:END:
+
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
+#+begin_src cpp
+
+#+end_src