The front door names its Markdown twin, and the twin is the front door (SEO-1) (#265)

ddiff --git a/server/agent-pages.js b/server/agent-pages.js
iindex c7e3751..6a8d5ec 100644
---- a/server/agent-pages.js
++++ b/server/agent-pages.js
@@@ -4,12 +4,13 @@
  // twin cannot drift from its page. Anonymous only; a run's page is a person's run and has no twin.
  const { renderPage } = require('./render/layout');
  
--function createAgentPages(ctx, publicViews) {
++function createAgentPages(ctx, publicViews, { home = null } = {}) {
      const views = publicViews;
      const twin = (page, path) => (page ? { html: renderPage({ ...page, viewer: { kind: 'anonymous' }, config: ctx.config, path }) } : null);
  
      async function renderPublicPage(path) {
--        if (path === '/') return twin(views.home(), path);
++        // / is the C4 front door a visitor gets (server/http/c4.js visitorHome), not the old marketing home.
++        if (path === '/') return twin((home && home()) || views.home(), path);
          if (path === '/start') return twin(views.start(), path);
          if (path === '/harnesses') return twin(views.harnesses(), path);
          if (path === '/improve') return twin(views.improve(), path);
ddiff --git a/server/app.js b/server/app.js
iindex 133ea82..63b44cc 100644
---- a/server/app.js
++++ b/server/app.js
@@@ -259,10 +259,11 @@ async function createApp(opts = {}) {
      // The agent layer (openvibe-shared/agent-layer): /.well-known/agent.json and the Markdown twins of the public
      // pages. The pages themselves keep their own routes — a signed-in visitor's account bar and forms are theirs
      // — so only the manifest and twin requests reach this mount; the pages advertise the twin themselves.
++    let c4Routes = null;   // created below, after the chat app's routes (the twin of / reads its front door)
      const agentLayer = express();
      require('openvibe-shared/agent-layer').mount(agentLayer, {
          descriptor: require('./agent-descriptor'),
--        render: require('./agent-pages').createAgentPages(ctx, pageRoutes.publicViews).renderPublicPage,
++        render: require('./agent-pages').createAgentPages(ctx, pageRoutes.publicViews, { home: () => c4Routes && c4Routes.visitorHome() }).renderPublicPage,
      });
      app.use((req, res, next) => {
          const twin = req.path.endsWith('.md') || req.query.format === 'markdown' || String(req.headers.accept || '').includes('text/markdown');
@@@ -273,7 +274,8 @@ async function createApp(opts = {}) {
      app.use(require('./http/chat').createChatRoutes(ctx));
      app.use(require('./http/git').createGitRoutes(ctx));   // after the chat app: it renders in ctx.chatShell
      // C4 workspace pages sit before the legacy marketing pages and share the existing owner-scoped task store.
--    app.use(require('./http/c4').createC4Routes(ctx));
++    c4Routes = require('./http/c4').createC4Routes(ctx);
++    app.use(c4Routes);
      app.use(pageRoutes);
      app.use(createRunRoutes({ config, store, sso, harnesses, run, tasks, sessions, keys, fetchImpl: fetchImpl || globalThis.fetch, log }));
      app.use((req, res) => send(res, 404, { viewer: req.viewer, config, path: req.originalUrl, title: 'Not found', body: html`<h1>Not found</h1><p>No page here. Try <a href="/harnesses">the agents</a>, <a href="/improve">Improve OpenVibe</a>, or the developer platform at <a href="https://openvibe.services">openvibe.services</a>.</p>` }));
ddiff --git a/server/http/c4.js b/server/http/c4.js
iindex d1ef085..0aa784c 100644
---- a/server/http/c4.js
++++ b/server/http/c4.js
@@@ -379,7 +379,7 @@ ${signedIn ? `<section class="c4-card c4-conductor-cta"><div class="c4-card-head
  <section class="c4-card"><div class="c4-card-head"><h2>Recent tasks</h2><a href="/tasks">View all</a></div>${rows.slice(0, 5).map(rowHtml).join('') || '<div class="c4-emptyline">No tasks yet. <a href="/#c4-prompt">Start a task</a></div>'}</section>
  ${signedIn && !mine.ok && mine.problem ? note(`Your machines could not be read, so the machine picker has only Auto. ${esc(mine.problem.detail || '')}`, 'bad') : ''}
  ${signedIn ? '' : `<section class="c4-reasons"><h2>Built for the way you work</h2><div class="c4-grid">${[['Any agent', 'Bring a key or plan. Auto picks a good fit and can hand over when one gets stuck.'], ['Your computer or ours', 'Pair your computer with one command. A hosted sandbox is coming soon.'], ['Proof you can inspect', 'See the changes, tests, screenshots and review before you approve.'], ['A cost you can follow', 'Track task costs and plan limits. Set caps that stop with a wrap-up.']].map(([a, b]) => `<article><h3>${a}</h3><p>${b}</p></article>`).join('')}</div></section>`}`;
--        if (!signedIn) return page(req, res, null, wrap(visitorHome()), { index: true, styles: [showcase.STYLESHEET], jsonLd: homeJsonLd(config) });
++        if (!signedIn) return page(req, res, null, wrap(visitorHome()), { index: true, agent: true, styles: [showcase.STYLESHEET], jsonLd: homeJsonLd(config) });
          page(req, res, null, wrap(content), {});
      });
  
@@@ -795,6 +795,9 @@ ${report.days.length ? `<div class="table-wrap" tabindex="0" role="region" aria-
      // module and borrow this one's kit (the page, the frame, the card, the pill, the flash and the same-origin check).
      r.use(require('./memory').createMemoryRoutes(ctx, { page, wrap, header, pill, flash, sameOrigin, viewer, form, signIn, note }));
  
++    // The front door a visitor gets at /, as a page for the layout: the Markdown twin of / is this page
++    // (server/agent-pages.js), so the twin says what a visitor reads (SEO-1; it was the old marketing home).
++    r.visitorHome = () => ({ css: ['css/c4.css'], scripts: ['js/c4.js'], body: raw(wrap(visitorHome())), index: true, agent: true, styles: [showcase.STYLESHEET], jsonLd: homeJsonLd(config) });
      return r;
  }
  
ddiff --git a/test/c4.test.js b/test/c4.test.js
iindex a1b07c2..6b92ec2 100644
---- a/test/c4.test.js
++++ b/test/c4.test.js
@@@ -32,6 +32,18 @@ const { boot, check, done } = require('./helpers/boot');
              assert.match(require('fs').readFileSync(require('path').join(__dirname, '..', 'server/http/c4.js'), 'utf8'), /if \(!signedIn\) return page\(req, res, null, wrap\(visitorHome\(\)\)/, 'the route sends a visitor to the front door');
          });
  
++        await check('the front door names its Markdown twin, and the twin is the front door (SEO-1)', async () => {
++            const home = await t.get('/');
++            assert.match(home.text, /<link rel="alternate" type="text\/markdown" href="https:\/\/openvibe\.codes\/index\.md">/, 'the head names the twin');
++            assert.match(String(home.headers.get('link') || ''), /<https:\/\/openvibe\.codes\/index\.md>; rel="alternate"; type="text\/markdown"/, 'so does the Link header');
++            const twin = await t.get('/index.md');
++            assert.strictEqual(twin.status, 200);
++            assert.match(String(twin.headers.get('content-type') || ''), /^text\/markdown/);
++            assert.ok(twin.text.includes('Every coding agent.') && twin.text.includes('Codex took over: Claude Code hit its plan limit'), 'the twin says what a visitor reads');
++            const mine = await t.get('/', { as: ada });
++            assert.ok(!/text\/markdown/.test(mine.text), 'a signed-in home names no twin');
++        });
++
          await check('task details are owner scoped and management pages honor sign-in', async () => {
              const settings = await t.get('/settings', { as: ada });
              assert.strictEqual(settings.status, 200);