feat: populate note files with problem descriptions and code stubs

Add populate-notes.mjs that fetches problem descriptions and
Python/C++ code stubs from LeetCode's GraphQL API. Populated
all 197 NeetCode 150 note files with:
- Problem description (examples, constraints)
- Python code stub (function signature)
- C++ code stub (function signature + includes)

API responses cached in leetcode/.cache/leetcode/ for instant re-runs.

org/study_deck_02/dsa/graphs/0802-find-eventual-safe-states.org

@@ -1,18 +1,69 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0802. Find Eventual Safe States :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0802. Find Eventual Safe States][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0802. Find Eventual Safe States][0802. Find Eventual Safe States]]
 :END:
 
+There is a directed graph of ~n~ nodes with each node labeled from ~0~ to ~n - 1~. The graph is represented by a *0-indexed* 2D integer array ~graph~ where ~graph[i]~ is an integer array of nodes adjacent to node ~i~, meaning there is an edge from node ~i~ to each node in ~graph[i]~.
+
+A node is a *terminal node* if there are no outgoing edges. A node is a *safe node* if every possible path starting from that node leads to a *terminal node* (or another safe node).
+
+Return /an array containing all the *safe nodes* of the graph/. The answer should be sorted in *ascending* order.
+
+*Example 1:*
+
+
+#+begin_src
+Input: graph = [[1,2],[2,3],[5],[0],[5],[],[]]
+Output: [2,4,5,6]
+Explanation: The given graph is shown above.
+Nodes 5 and 6 are terminal nodes as there are no outgoing edges from either of them.
+Every path starting at nodes 2, 4, 5, and 6 all lead to either node 5 or 6.
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: graph = [[1,2,3,4],[1,2],[3,4],[0,4],[]]
+Output: [4]
+Explanation:
+Only node 4 is a terminal node, and every path starting at node 4 leads to node 4.
+#+end_src
+
+
+*Constraints:*
+
+ - ~n == graph.length~
+
+ - ~1 <= n <= 10^{4}~
+
+ - ~0 <= graph[i].length <= n~
+
+ - ~0 <= graph[i][j] <= n - 1~
+
+ - ~graph[i]~ is sorted in a strictly increasing order.
+
+ - The graph may contain self-loops.
+
+ - The number of edges in the graph will be in the range ~[1, 4 * 10^{4}]~.
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def eventualSafeNodes(self, graph: List[List[int]]) -> List[int]:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    vector<int> eventualSafeNodes(vector<vector<int>>& graph) {
+        
+    }
+};
 #+end_src