docs(changelog): link problems using short redirects instead of issue URLs

apps/docs/pages/changelog.astro

@@ -8,6 +8,8 @@
  */
 import PageLayout from "blume/components/layout/PageLayout.astro";
 import data from "blume:data";
+import { withBase } from "blume/components/islands/base-path.ts";
+import redirects from "../redirects";
 import { readReleases } from "../lib/releases.ts";
 
 const { config } = data;
@@ -19,6 +21,14 @@ const DATE = new Intl.DateTimeFormat("en-US", {
   year: "numeric",
 });
 const issueUrl = (n: number) => `https://github.com/prdlk/leetcode/issues/${n}`;
+// LC number -> its docs page route, off sync's `/<num>` short links — the
+// page itself, not the redirect, so a click is one hop. A problem with no page
+// (none yet) links to its issue instead.
+const pages = new Map(redirects.map((r) => [Number(r.from.slice(1)), r.to]));
+const problemHref = (lc: number, issue: number) => {
+  const route = pages.get(lc);
+  return route ? withBase(route) : issueUrl(issue);
+};
 // The /progress cards' difficulty palette (--chart-1..3 in theme.css), so a
 // Hard reads the same colour here as in the SolvedRing gauge.
 const DIFFICULTY: Record<string, { label: string; class: string }> = {
@@ -84,8 +94,7 @@ const description = "Every topic and review the campaign finished, newest first.
                     <span class="select-none text-border" aria-hidden="true">—</span>
                     <span class="min-w-0">
                       <span class="mr-2 font-mono text-xs uppercase tracking-wide">{p.set}</span>
-                      {/* The problem's docs page; its issue only until it has one. */}
-                      <a class="text-foreground no-underline hover:underline" href={p.docs ?? issueUrl(p.issue)}>
+                      <a class="text-foreground no-underline hover:underline" href={problemHref(p.lc, p.issue)}>
                         {p.title}
                       </a>
                       {DIFFICULTY[p.difficulty] && (