feat(docs): add changelog page and switch tag guide paths to appendix

apps/docs/lib/releases.ts

@@ -0,0 +1,94 @@
+/**
+ * The `/changelog` page's data: every timever release apps/cli/release-topics.ts
+ * published — one per finished topic and per finished `Review <N>` issue —
+ * read from the GitHub API at build time (pages/changelog.astro awaits it).
+ *
+ * One page, no per-release subpages: each release becomes one timeline card,
+ * so the fields come from the release itself rather than a staged content
+ * entry. The date is the timever tag (`YYYYMMDD.HHMMSS.NNNNNNNNN`, UTC — the
+ * instant the last required problem closed), never `published_at`, which the
+ * API cannot backdate and which reads the backfill day for every old release.
+ * The problems are the rows of the body's `### Closed …` tables, the shape
+ * release-topics.ts's render() writes: `| #issue | LC n · Name | set | diff |
+ * closed | [py](…) · [docs](…) |`. Only `### Closed …` sections are read, so
+ * a release published before open problems were dropped from the body still
+ * shows only what finished.
+ *
+ * Auth: GITHUB_TOKEN when set (deploy.yml passes it), else unauthenticated —
+ * one request per 100 releases fits the anonymous limit. A failed request
+ * fails the build: a changelog silently missing its releases is worse.
+ */
+
+const REPO = "prdlk/leetcode";
+const MARKER = /<!-- release-topics: #(\d+) -->/u;
+const TIMEVER = /^(\d{4})(\d{2})(\d{2})\.(\d{2})(\d{2})(\d{2})\.\d{9}$/u;
+const KIND = /^(Topic|Review) \d+ — /u;
+
+export interface ReleaseProblem {
+  issue: number;
+  /** `LC 57 · Insert Interval`. */
+  title: string;
+  set: string;
+  /** `easy` / `medium` / `hard`, the problem's `diff:*` label. */
+  difficulty: string;
+  /** The problem's `/<num>` docs short link, once it has a page. */
+  docs?: string;
+}
+
+export interface Release {
+  /** Topic or Review issue the release records. */
+  issue: number;
+  name: string;
+  kind: "Topic" | "Review";
+  /** UTC instant the last required problem closed, from the timever tag. */
+  finishedAt: Date;
+  url: string;
+  problems: ReleaseProblem[];
+}
+
+/** Rows of every `### Closed …` table in a release body. */
+function closedProblems(body: string): ReleaseProblem[] {
+  const problems: ReleaseProblem[] = [];
+  let closed = false;
+  for (const line of body.split("\n")) {
+    if (line.startsWith("### ")) closed = line.startsWith("### Closed");
+    if (!closed || !line.startsWith("| #")) continue;
+    const [issue, title, set, difficulty, , solution] = line.slice(1, -1).split("|").map((cell) => cell.trim());
+    if (!issue || !title || !set || !difficulty) continue;
+    problems.push({
+      issue: Number(issue.slice(1)),
+      title,
+      set,
+      difficulty,
+      docs: solution?.match(/\[docs\]\(([^)]+)\)/u)?.[1],
+    });
+  }
+  return problems;
+}
+
+export async function readReleases(): Promise<Release[]> {
+  const headers: Record<string, string> = { accept: "application/vnd.github+json" };
+  if (process.env.GITHUB_TOKEN) headers.authorization = `Bearer ${process.env.GITHUB_TOKEN}`;
+  const releases: Release[] = [];
+  for (let page = 1; ; page++) {
+    const res = await fetch(`https://api.github.com/repos/${REPO}/releases?per_page=100&page=${page}`, { headers });
+    if (!res.ok) throw new Error(`GET ${REPO} releases -> ${res.status} ${await res.text()}`);
+    const batch = (await res.json()) as { tag_name: string; name: string | null; body: string | null; html_url: string }[];
+    for (const r of batch) {
+      const issue = r.body?.match(MARKER)?.[1];
+      const t = r.tag_name.match(TIMEVER);
+      const kind = r.name?.match(KIND)?.[1];
+      if (!issue || !t || !kind || !r.name || !r.body) continue;
+      releases.push({
+        issue: Number(issue),
+        name: r.name,
+        kind: kind as Release["kind"],
+        finishedAt: new Date(`${t[1]}-${t[2]}-${t[3]}T${t[4]}:${t[5]}:${t[6]}Z`),
+        url: r.html_url,
+        problems: closedProblems(r.body),
+      });
+    }
+    if (batch.length < 100) break;
+  }
+  return releases.sort((a, b) => b.finishedAt.getTime() - a.finishedAt.getTime());
+}