Shared links unfurl: per-route OG meta for match and team pages

Crawler-visible <title> + og:title/description are injected into the
SPA shell server-side: match links carry the score or the model's
probability split, team links the current title odds — honest framing
included. Plain shell for every other route.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/src/index.ts

@@ -1,5 +1,5 @@
 import path from 'node:path';
-import { existsSync } from 'node:fs';
+import { existsSync, readFileSync } from 'node:fs';
 import Fastify from 'fastify';
 import type { FastifyRequest } from 'fastify';
 import fastifyWebsocket from '@fastify/websocket';
@@ -184,12 +184,53 @@ export function buildServer() {
   }, 24 * 60 * 60 * 1000);
   app.addHook('onClose', async () => clearInterval(refitTimer));
 
-  // ---- static SPA (prod) with history fallback ----
+  // ---- static SPA (prod) with history fallback + per-route OG meta ----
   if (existsSync(STATIC_DIR)) {
     void app.register(fastifyStatic, { root: STATIC_DIR, wildcard: false });
+
+    // Shared links unfurl with the model's numbers: swap <title> and inject
+    // og: meta for /match/:num and /team/:name before serving the SPA shell.
+    const indexHtml = readFileSync(`${STATIC_DIR}/index.html`, 'utf8');
+    const esc = (s: string): string => s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/"/g, '&quot;');
+    const withMeta = (title: string, desc: string): string =>
+      indexHtml.replace(
+        /<title>[^<]*<\/title>/,
+        `<title>${esc(title)}</title>\n    <meta property="og:title" content="${esc(title)}" />\n    <meta property="og:description" content="${esc(desc)}" />\n    <meta name="description" content="${esc(desc)}" />`,
+      );
+    const ogFor = (url: string): string | null => {
+      try {
+        const mMatch = /^\/match\/(\d+)(?:\?|$)/.exec(url);
+        if (mMatch) {
+          const f = state.allFixtures().find((x) => x.num === Number(mMatch[1]));
+          if (!f) return null;
+          const pred = model.current().matches.find((m) => m.num === f.num);
+          const score = f.homeScore != null && f.status !== 'scheduled' ? ` ${f.homeScore}–${f.awayScore}` : '';
+          const odds = pred ? ` · Model: ${Math.round(pred.probs.home * 100)}/${Math.round(pred.probs.draw * 100)}/${Math.round(pred.probs.away * 100)}` : '';
+          return withMeta(
+            `${f.home.label}${score || ' vs'} ${f.away.label} — Cup26`,
+            `World Cup 2026 · ${f.venue}${odds} (model probabilities, not betting advice)`,
+          );
+        }
+        const mTeam = /^\/team\/([^/?]+)(?:\?|$)/.exec(url);
+        if (mTeam) {
+          const team = decodeURIComponent(mTeam[1]!);
+          const odds = model.current().odds.find((o) => o.team === team);
+          if (!odds) return null;
+          return withMeta(
+            `${team} — Cup26`,
+            `World Cup 2026 · title odds ${(odds.champion * 100).toFixed(1)}% by the Cup26 model`,
+          );
+        }
+      } catch { /* fall through to the plain shell */ }
+      return null;
+    };
+
     app.setNotFoundHandler((req, reply) => {
-      if (req.raw.url?.startsWith('/ws')) return reply.code(426).send('Upgrade Required');
-      if (req.raw.url?.startsWith('/api')) return reply.code(404).send({ error: 'not found' });
+      const url = req.raw.url ?? '/';
+      if (url.startsWith('/ws')) return reply.code(426).send('Upgrade Required');
+      if (url.startsWith('/api')) return reply.code(404).send({ error: 'not found' });
+      const html = ogFor(url);
+      if (html) return reply.type('text/html; charset=utf-8').send(html);
       return reply.sendFile('index.html');
     });
   }