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

leetcode/AGENTS.md

@@ -68,9 +68,28 @@ Arrays & Hashing
 ## Org-Mode Format
 
 Each topic is a `* TODO` heading with a `[/]` cookie for progress.
-Problems are `- [ ] TODO` items with difficulty tags (`:easy:`,
-`:medium:`, `:hard:`). Python and C++ solution links are nested
-`- [ ] TODO` sub-items. LeetCode and video links are plain list items.
+Problems are `** TODO` sub-headings with difficulty tags (`:easy:`,
+`:medium:`, `:hard:`). Python and C++ solution links are `***` sub-headings
+under each problem. Each problem also links to a notes file at
+`org/cpp/dsa/<topic>/<problem>.org` for personal solutions and flashcards.
+
+### Notes Files
+
+`org/cpp/dsa/<topic>/<code>.org` — one per NeetCode 150 problem (199 total).
+Scaffolded by `scaffold-notes.mjs`. Template:
+
+```org
+* TODO 0217. Contains Duplicate :easy:
+:PROPERTIES:
+:NEETCODE: [[../../../../leetcode/out/roadmap.org::*0217. Contains Duplicate][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src
+```
+
+Run `node scaffold-notes.mjs` to create missing note files (skips existing).
 
 ## Updating
 

leetcode/extract.mjs

@@ -207,10 +207,19 @@ function buildOrg(sortedNodes, problemsByTopic) {
   const difficultyTag = (d) =>
     d === "Easy" ? "easy" : d === "Medium" ? "medium" : "hard";
 
+  const topicSlug = (name) =>
+    name
+      .toLowerCase()
+      .replace(/[^a-z0-9]+/g, "-")
+      .replace(/(^-|-$)/g, "");
+
+  const notesRoot = "../../org/cpp/dsa";
+
   for (const node of sortedNodes) {
     const topicProblems = (problemsByTopic[node.name] || []).filter(
       (p) => p.neetcode150
     );
+    const slug = topicSlug(node.name);
     lines.push(`* TODO ${node.name} [/]`);
     lines.push("");
 
@@ -224,14 +233,18 @@ function buildOrg(sortedNodes, problemsByTopic) {
       const tag = difficultyTag(p.difficulty);
       const lcUrl = `${LEETCODE_BASE}${p.link}`;
       const num = p.code.split("-")[0];
+      const notesFile = `${notesRoot}/${slug}/${p.code}.org`;
       lines.push(`** TODO ${num}. ${p.name} :${tag}:`);
-      lines.push(`- Python: [[${GITHUB_SOLUTIONS}python/${p.code}.py][${p.code}.py]]`);
-      lines.push(`- C++: [[${GITHUB_SOLUTIONS}cpp/${p.code}.cpp][${p.code}.cpp]]`);
+      lines.push(`*** Python`);
+      lines.push(`- [[${GITHUB_SOLUTIONS}python/${p.code}.py][${p.code}.py]]`);
+      lines.push(`*** C++`);
+      lines.push(`- [[${GITHUB_SOLUTIONS}cpp/${p.code}.cpp][${p.code}.cpp]]`);
       lines.push(`- LeetCode: [[${lcUrl}][${p.link}]]`);
       if (p.video)
         lines.push(
           `- Video: [[https://youtube.com/watch?v=${p.video}][explanation]]`
         );
+      lines.push(`- Notes: [[${notesFile}][My Solution]]`);
     }
     lines.push("");
   }

leetcode/scaffold-notes.mjs

@@ -0,0 +1,55 @@
+import { readFileSync, writeFileSync, existsSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+const roadmap = readFileSync(join(__dirname, "out/roadmap.org"), "utf8");
+const dsaDir = join(__dirname, "../org/cpp/dsa");
+
+const topicSlug = (name) =>
+  name
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, "-")
+    .replace(/(^-|-$)/g, "");
+
+let currentTopic = "";
+let count = 0;
+
+for (const line of roadmap.split("\n")) {
+  const topicMatch = line.match(/^\* TODO (.+?) \[/);
+  if (topicMatch) {
+    currentTopic = topicSlug(topicMatch[1]);
+    continue;
+  }
+
+  const problemMatch = line.match(
+    /^\*\* TODO (\d+)\. (.+?) :(easy|medium|hard):$/
+  );
+  if (problemMatch) {
+    const [, num, name, diff] = problemMatch;
+    const slug = name
+      .toLowerCase()
+      .replace(/[^a-z0-9]+/g, "-")
+      .replace(/(^-|-$)/g, "");
+    const code = `${num}-${slug}`;
+    const filePath = join(dsaDir, currentTopic, `${code}.org`);
+
+    if (existsSync(filePath)) continue;
+
+    const relPath = `../../../../leetcode/out/roadmap.org::*${num}. ${name}`;
+    const content = `* TODO ${num}. ${name} :${diff}:
+:PROPERTIES:
+:NEETCODE: [[${relPath}][Roadmap]]
+:END:
+
+#+begin_src cpp
+
+#+end_src
+`;
+    writeFileSync(filePath, content);
+    count++;
+  }
+}
+
+console.log(`Created ${count} note files`);