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/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`);