feat(cli): sync LeetCode topic tags, generate guide placeholders, and write video frontmatter instead of embeds

apps/cli/videos.ts

@@ -2,24 +2,23 @@
 /**
  * Find the NeetCode explanation video for every docs page that has none.
  *
- * A finished solution page ends with `## Explanation` holding one
- * `<YouTube id="…" title="…" />` — NeetCode's walkthrough of the problem.
- * `sync.ts` never writes that section (it owns only `## Solution`), so pages
- * accumulate without one. This script lists every numbered page lacking a
- * `<YouTube` embed and looks each up on NeetCode's two channels, main channel
- * first, accepting only a title that names the page's exact LC number
- * (`… - Leetcode 226 - …`) and is not a #short. No YouTube API key: the
- * channel search page embeds its results as `ytInitialData` JSON, which is
- * all we parse. Ranking is the channel's own — the first exact-number match
- * wins.
+ * A finished solution page carries frontmatter `video: <YouTube id>` —
+ * NeetCode's walkthrough of the problem — which the docs `PageHeader` slot
+ * (`apps/docs/components/ProblemBadges.astro`) renders as the red
+ * "Explanation" badge beside the topic badges. `sync.ts` never writes that key
+ * (it owns `icon:`, `topics:` and `## Solution`), so pages accumulate without
+ * one. This script lists every numbered page lacking `video:` and looks each
+ * up on NeetCode's two channels, main channel first, accepting only a title
+ * that names the page's exact LC number (`… - Leetcode 226 - …`) and is not a
+ * #short. No YouTube API key: the channel search page embeds its results as
+ * `ytInitialData` JSON, which is all we parse. Ranking is the channel's own —
+ * the first exact-number match wins.
  *
  *   bun apps/cli/videos.ts           # report: page → video (or "no match")
- *   bun apps/cli/videos.ts --write   # also append `## Explanation` + embed
+ *   bun apps/cli/videos.ts --write   # also add `video:` to the frontmatter
  *
- * --write appends at end of file (below `## Solution`, where sync.ts leaves
- * human sections alone) and adds the `## Explanation` heading only when the
- * page lacks it. A page with no match is left untouched, so re-runs are
- * no-ops once every page has its embed.
+ * --write inserts the key before `sidebar:`. A page with no match is left
+ * untouched, so re-runs are no-ops once every page has its video.
  */
 import { join } from "node:path";
 
@@ -126,23 +125,21 @@ interface Page {
   text: string;
 }
 
-/** Numbered solution pages without a `<YouTube` embed, by LC number. */
+/** The page's frontmatter block, `---` to `---`. */
+const FRONTMATTER = /^---\n[\s\S]*?\n---/;
+
+/** Numbered solution pages without a `video:` key, by LC number. */
 async function pagesMissingVideo(): Promise<Page[]> {
   const pages: Page[] = [];
   for (const rel of await Array.fromAsync(new Bun.Glob("**/*.mdx").scan(DOCS))) {
     const text = await Bun.file(join(DOCS, rel)).text();
     const t = text.match(/^title: '(\d+)\./m);
-    if (t && !text.includes("<YouTube")) pages.push({ num: Number(t[1]), rel, text });
+    const fm = text.match(FRONTMATTER)?.[0] ?? "";
+    if (t && !/^video:/m.test(fm)) pages.push({ num: Number(t[1]), rel, text });
   }
   return pages.sort((a, b) => a.num - b.num);
 }
 
-function withEmbed(page: Page, video: Video): string {
-  const embed = `<YouTube id="${video.id}" title="${video.title.replaceAll('"', "'")}" />`;
-  const heading = /^## Explanation\s*$/m.test(page.text) ? "" : "## Explanation\n\n";
-  return `${page.text.replace(/\s*$/, "\n")}\n${heading}${embed}\n`;
-}
-
 // ── main ─────────────────────────────────────────────────────────
 
 const missing = await pagesMissingVideo();
@@ -162,7 +159,8 @@ for (const page of missing) {
   found++;
   let status = "";
   if (WRITE) {
-    await Bun.write(join(DOCS, page.rel), withEmbed(page, video));
+    const next = page.text.replace(FRONTMATTER, (fm) => fm.replace(/^sidebar:$/m, `video: ${JSON.stringify(video.id)}\nsidebar:`));
+    await Bun.write(join(DOCS, page.rel), next);
     status = "written";
   }
   rows.push([page.rel, `https://youtu.be/${video.id}`, `${video.title} (${video.channel})`, status]);