feat(sync): organize solution docs by category and add sidebar labels

.omp/commands/sync-solutions.md

@@ -2,7 +2,7 @@
 description: Sync work/ leetcode solutions into docs/solutions/ pages (gold standard format)
 ---
 
-Sync every leetcode solution under `work/` into a docs page under `docs/solutions/`, formatted like the gold standard `docs/solutions/344-reverse-string.mdx`. Extra focus (optional): $@
+Sync every leetcode solution under `work/` into a docs page under `docs/solutions/`, formatted like the gold standard `docs/solutions/(two-pointers)/344-reverse-string.mdx`. Extra focus (optional): $@
 
 ## Run the script
 
@@ -16,12 +16,13 @@ bun run sync
 
 - Globs `work/**/*.{js,py}` (`<number>.<kebab-slug>.{js,py}` under `work/<Difficulty>/<Category>/`) and groups the two language variants of a problem by leetcode number.
 - Parses each file's header comment (js block comment / py docstring) into title, difficulty, statement, examples, constraints, and follow-up.
-- New problems get a full page at `docs/solutions/<leetcode-number>-<kebab-slug>.mdx`: frontmatter, `<Badge>` topic (README curriculum table, falling back to the `work/` subdirectory), `::::warning` for follow-ups/special requirements, examples, constraints, and the solution code verbatim.
+- New problems get a full page at `docs/solutions/(<category>)/<leetcode-number>-<kebab-slug>.mdx`: frontmatter, `<Badge>` topic (README curriculum table, falling back to the `work/` subdirectory), `::::warning` for follow-ups/special requirements, examples, constraints, and the solution code verbatim.
-- The filename prefix is the leetcode problem number — it orders the sidebar numerically and is stripped from the URL (`344-reverse-string.mdx` → `/solutions/reverse-string`). The script renames any page whose filename drifts from `<leetcode-number>-<kebab-slug>.mdx`.
+- `(<category>)` is the kebab-cased `work/` subdirectory (`(array)`, `(hash-table)`, `(two-pointers)`, …) and becomes the sidebar group; the leetcode-number filename prefix orders pages numerically. Both are stripped from the URL (`(two-pointers)/344-reverse-string.mdx` → `/solutions/reverse-string`). The script moves any page whose path drifts from this scheme.
+- Frontmatter `title` keeps the number (`'344. Reverse String'`); `sidebar.label` is the number-free problem name. The script backfills a missing `sidebar.label` on existing pages but never overwrites one.
 - Already-ported pages (frontmatter title starts with the leetcode number) only get their `## Solution` section regenerated — curated prose is never touched.
 - Problems solved in both languages render as a `<CodeGroup>` (Python first, then JavaScript); single-language solutions render as a plain fence.
 
-The script prints the report table: work file → docs page → created / renamed / updated / skipped (already in sync).
+The script prints the report table: work file → docs page → created / moved / updated / skipped (already in sync).
 
 ## Review
 

scripts/sync.ts

@@ -10,7 +10,7 @@
  *   renders as a <CodeGroup> (Python first); single-language solutions
  *   render as a plain fence.
  */
-import { readdir, rename } from "node:fs/promises";
+import { mkdir, rename } from "node:fs/promises";
 import { basename, join } from "node:path";
 
 const ROOT = join(import.meta.dir, "..");
@@ -284,6 +284,7 @@ function renderPage(sol: Solution, topic: string): string {
     `title: '${h.num}. ${h.title.replaceAll("'", "''")}'`,
     /[:#]/.test(description) ? `description: '${description.replaceAll("'", "''")}'` : `description: ${description}`,
     "sidebar:",
+    `  label: '${h.title.replaceAll("'", "''")}'`,
     `  badge: '${h.difficulty}'`,
     "---",
     "",
@@ -346,12 +347,20 @@ for await (const rel of new Bun.Glob("**/*.{js,py}").scan(WORK)) {
 
 const topics = await readmeTopics();
 
+/** Insert a number-free `sidebar.label` into existing frontmatter when missing. */
+function ensureLabel(page: string, h: Header): string {
+  const fm = page.match(/^---\n[\s\S]*?\n---/);
+  if (!fm || /^ {2}label: /m.test(fm[0])) return page;
+  const label = `  label: '${h.title.replaceAll("'", "''")}'`;
+  return page.replace(/^sidebar:$/m, `sidebar:\n${label}`);
+}
+
 // Existing docs pages, keyed by leetcode number from the frontmatter title.
-const pages = new Map<number, string>(); // num -> filename
+const pages = new Map<number, string>(); // num -> path relative to DOCS
-for (const f of (await readdir(DOCS)).filter((f) => f.endsWith(".mdx")).sort()) {
+for (const rel of (await Array.fromAsync(new Bun.Glob("**/*.mdx").scan(DOCS))).sort()) {
-  const text = await Bun.file(join(DOCS, f)).text();
+  const text = await Bun.file(join(DOCS, rel)).text();
   const t = text.match(/^title: '(\d+)\./m);
-  if (t) pages.set(Number(t[1]), f);
+  if (t) pages.set(Number(t[1]), rel);
 }
 
 const report: [string, string, string][] = [];
@@ -360,8 +369,11 @@ const ordered = [...solutions.values()].sort((a, b) => a.num - b.num);
 for (const sol of ordered) {
   const langs = Object.keys(sol.code).sort().join("+");
   const workRef = `${sol.num}.${sol.slug} (${langs})`;
-  const name = `${sol.num}-${sol.slug}.mdx`; // prefix = leetcode number (numeric sidebar order, stripped from the URL)
+  // (category) group folder + leetcode-number prefix: numeric sidebar order, both stripped from the URL.
+  const group = `(${sol.category.toLowerCase().replaceAll(" ", "-")})`;
+  const name = `${group}/${sol.num}-${sol.slug}.mdx`;
   const existing = pages.get(sol.num);
+  await mkdir(join(DOCS, group), { recursive: true });
 
   if (existing) {
     const page = await Bun.file(join(DOCS, existing)).text();
@@ -370,15 +382,15 @@ for (const sol of ordered) {
       report.push([workRef, existing, "ERROR: no '## Solution' heading"]);
       continue;
     }
-    const next = page.slice(0, at) + solutionSection(sol);
+    const next = ensureLabel(page.slice(0, at) + solutionSection(sol), sol.header);
     const actions: string[] = [];
     if (existing !== name) {
       await rename(join(DOCS, existing), join(DOCS, name));
-      actions.push("renamed");
+      actions.push("moved");
     }
     if (next !== page) {
       await Bun.write(join(DOCS, name), next);
-      actions.push("updated (solution)");
+      actions.push("updated");
     }
     report.push([workRef, name, actions.join(" + ") || "skipped (in sync)"]);
   } else {