Server-render the site navigation in the first HTML (#281)

ddiff --git a/server/ui/layout.js b/server/ui/layout.js
iindex f00b26f..c3871b6 100644
---- a/server/ui/layout.js
++++ b/server/ui/layout.js
@@@ -1,5 +1,6 @@
  'use strict';
  const ovServe = require('openvibe-shared/serve');
++const frame = require('openvibe-shared/frame');
  const seo = require('openvibe-shared/seo');
  const social = require('openvibe-shared/social');
  const { TWIN_PATH_RE } = require('../agent-pages');
@@@ -204,8 +205,7 @@ ${[...new Set(['showcase.css', 'kit.css', 'kit-data.css', ...styles])].map((name
  <script src="${ovServe.url('footer.js')}" defer></script>
  </head>
  <body>
--<div id="navbar-mount"></div>
--<noscript><nav class="ore" style="padding:8px 16px"><a href="/">OpenRestream</a> · <a href="/streams">Streams</a> · <a href="/sessions">Sessions</a> · ${user ? '<a href="/auth/logout">Sign out</a>' : '<a href="/auth/login">Sign in</a>'}</nav></noscript>
++${frame.serverNav({ name: SITE, service: 'openre', home: '/', links: nav.links })}
  <main id="main" class="ore">
  ${body}
  </main>
ddiff --git a/test/destinations-ui.test.js b/test/destinations-ui.test.js
iindex 353bc99..1d9dd6c 100644
---- a/test/destinations-ui.test.js
++++ b/test/destinations-ui.test.js
@@@ -55,7 +55,10 @@ t('the UI works without JavaScript: landing, sign-in prompt, streams', async ()
      assert.strictEqual(home.status, 200);
      assert.match(home.text, /OpenRestream/);
      assert.match(home.text, /theme-loader\.js/);
--    assert.match(home.text, /<noscript><nav/);
++    // The first HTML carries the site navigation inside the mount (the browser navbar replaces it on boot).
++    const serverNav = /<div id="navbar-mount"><nav[^>]*data-ov-server-nav="true"[\s\S]*?<\/nav><\/div>/.exec(home.text);
++    assert.ok(serverNav, 'the first HTML has the server navigation');
++    assert.match(serverNav[0], /href="\/streams"[^>]*>Streams</);
      const signin = await request(api.base, 'GET', '/streams');
      assert.strictEqual(signin.status, 401);
      assert.match(signin.text, /Sign in with OpenVibe/);
ddiff --git a/test/discovery.test.js b/test/discovery.test.js
iindex 1581bb3..5b2fb34 100644
---- a/test/discovery.test.js
++++ b/test/discovery.test.js
@@@ -109,6 +109,11 @@ t('the front page leads with open restreaming, links to Live for browser go-live
          const r = await request(api.base, 'GET', '/');
          assert.strictEqual(r.status, 200);
          assert.match(r.text, /<h1>Go live once\. Stream everywhere\.<\/h1>/);
++        // The first HTML carries the site's navigation, not only the scripts that draw it.
++        const serverNav = /<div id="navbar-mount"><nav class="openvibe-navbar"[^>]*data-ov-server-nav="true"[\s\S]*?<\/nav><\/div>/.exec(r.text);
++        assert.ok(serverNav, 'the first HTML has the server navigation');
++        assert.match(serverNav[0], /href="\/streams"[^>]*>Streams</);
++        assert.match(serverNav[0], /href="\/go-live"[^>]*>Go live</);
          assert.match(r.text, /ovk-page-head/);
          // The hero's signal flow (11-07): every platform with its own switch, the count by CSS, no script needed.
          const flow = (/<div class="ore-flow"[\s\S]*?<\/ul>/.exec(r.text) || [''])[0];