A live channel's shared link shows the stream as it is now and says "Live now" (it showed the avatar); the person's structured data keeps the avatar and bio (#274)

ddiff --git a/server/seo/pages.js b/server/seo/pages.js
iindex ad796af0..0337562f 100644
---- a/server/seo/pages.js
++++ b/server/seo/pages.js
@@@ -286,12 +286,17 @@ async function _channelMeta(username, page = 1) {
      const canonicalPath = page > 1 && !pastEnd ? `${basePath}?page=${page}` : basePath;
      const pageLabel = page > 1 ? ` — videos, page ${page}` : '';
  
--    const desc = clean(bio || aiShort || `${name} (${handle}) streams live on ${SITE_NAME}. Watch their live streams, VODs and clips.`, 200);
--    const image = acct.avatarUrl ? abs(acct.avatarUrl) : DEFAULT_OG_IMAGE;
++    const about = clean(bio || aiShort || `${name} (${handle}) streams live on ${SITE_NAME}. Watch their live streams, VODs and clips.`, 200);
++    const avatar = acct.avatarUrl ? abs(acct.avatarUrl) : null;
++    // A live channel's shared link shows the stream as it is now (16:9) and says so; offline, the avatar. The page is
++    // kept a minute (CHANNEL_CACHE_MS), so the card follows the stream going live or ending.
++    const liveNow = live.length ? live[0] : null;
++    const image = (liveNow && liveNow.thumbnail_url ? abs(liveNow.thumbnail_url) : null) || avatar || DEFAULT_OG_IMAGE;
++    const desc = liveNow ? clean(`Live now: ${liveNow.title || `${name} is streaming`}. ${about}`, 200) : about;
      const person = {
          '@type': 'Person', name: clean(name, 80), alternateName: handle, url: abs(basePath),
--        image: image !== DEFAULT_OG_IMAGE ? image : undefined,
--        description: desc,
++        image: avatar || undefined,
++        description: about,
          interactionStatistic: followers ? { '@type': 'InteractionCounter', interactionType: 'https://schema.org/FollowAction', userInteractionCount: followers } : undefined,
      };
      const profile = { ...seo.jsonLd.webPage({ type: 'ProfilePage', name: `${name} (${handle})`, url: abs(canonicalPath) }), mainEntity: person };
ddiff --git a/test/seo-ssr.test.js b/test/seo-ssr.test.js
iindex eb4810c2..a752d49d 100644
---- a/test/seo-ssr.test.js
++++ b/test/seo-ssr.test.js
@@@ -244,6 +244,20 @@ const server = http.createServer(app).listen(0, '127.0.0.1', async () => {
          }
      });
  
++    await check('a live channel\'s shared link shows the stream as it is now and says so; the person keeps their avatar', async () => {
++        await addUser(6, 'carol', 'Carol', 'I paint.');
++        await db.run("UPDATE users SET avatar_url = 'https://openvibe.media/avatars/carol.png' WHERE id = 6");
++        await db.run("INSERT INTO streams (user_id, title, protocol, is_live, thumbnail_url, started_at, last_heartbeat) VALUES (6, 'Painting a sunset', 'webrtc', 1, '/api/thumbnails/stream-9-1.jpg', ov_now(), ov_now())");
++        const html = (await get('/@carol')).body;
++        assert.ok(head(html).includes('<meta property="og:image" content="https://openvibe.live/api/thumbnails/stream-9-1.jpg">'), 'the live picture');
++        assert.match(head(html), /<meta property="og:description" content="Live now: Painting a sunset\. I paint\.">/);
++        const person = ldOf(html).flatMap((n) => (n['@graph'] || [n])).find((n) => n['@type'] === 'Person' || (n.mainEntity && n.mainEntity['@type'] === 'Person'));
++        const p = person && (person['@type'] === 'Person' ? person : person.mainEntity);
++        assert.ok(p, 'a Person node');
++        assert.strictEqual(p.image, 'https://openvibe.media/avatars/carol.png', 'the person is still pictured by their avatar');
++        assert.strictEqual(p.description, 'I paint.', 'and described by their bio');
++    });
++
      await check('the home page\'s JSON-LD lists are named by the snapshot\'s visible headings', async () => {
          const home = (await get('/')).body;
          const lists = ldOf(home).filter((n) => n['@type'] === 'ItemList');