Machines page: make a spare computer a desk host (the --desk-host install, one click away), and each machine says what desks it runs for its agents (#183)

ddiff --git a/server/web/render.js b/server/web/render.js
iindex a4923b0..8f244d1 100644
---- a/server/web/render.js
++++ b/server/web/render.js
@@@ -720,8 +720,11 @@ function renderMachinesPage({ machines = [], pairing = null }) {
          const c = (m.capabilities && typeof m.capabilities === 'object' ? m.capabilities : {}).computer;
          if (!c || typeof c !== 'object') return null;
          const level = m.computer_level || ((c.files || c.terminal || c.screen || {}).level) || null;
++        const d = c.desk && typeof c.desk === 'object' ? c.desk : null;
          return { level: LEVELS[level] ? level : null, terminal: !!c.terminal, files: !!c.files, screen: !!c.screen, probe: !!c.probe, input: !!c.input,
--            screenStream: !!(c.screen && c.screen.stream === true) };
++            screenStream: !!(c.screen && c.screen.stream === true),
++            // Desks for its agents (Desks plan): how many at once, which kinds, and whether sign-ins carry over.
++            desks: d ? { max: Number.isInteger(d.max_desks) ? d.max_desks : 1, kinds: Array.isArray(d.kinds) ? d.kinds : ['desktop'], keeps: d.profiles === true } : null };
      };
      // Vibe by voice: shown for a machine whose Node runs the voice plugin (capabilities.voice).
      const voiceRow = (m) => {
@@@ -734,13 +737,21 @@ function renderMachinesPage({ machines = [], pairing = null }) {
                  : `<form method="post" action="/machines/${esc(m.id)}/voice" class="inline-form"><input type="hidden" name="on" value="1"><label class="sr-only" for="cw-${esc(m.id)}">Call word</label><input id="cw-${esc(m.id)}" name="call_word" maxlength="40" value="${esc(word)}" aria-label="Call word"><button type="submit" class="button quiet" aria-pressed="false">Let Vibe answer my voice here</button></form>`)
              + '<span class="muted">The machine listens for its call word on its own; only what you say after it goes to Vibe, and the answer is spoken here and kept in your Vibe chats.</span></div>';
      };
++    // "Desks for your agents: 4 at once (browser desks count as half), sign-ins kept"
++    const deskWords = (d) => {
++        const browser = d.kinds.includes('browser');
++        const whole = d.kinds.includes('desktop');
++        const kinds = browser && whole ? `${d.max} at once, or twice as many browser desks` : browser ? `${d.max * 2} browser desks at once` : `${d.max} at once`;
++        return `Desks for your agents: ${kinds}${d.keeps ? ', sign-ins kept' : ''}`;
++    };
      const computerRow = (m) => {
          const c = computerOf(m);
          if (!c) return '';
          const can = [c.terminal && 'terminal', c.files && 'files', c.screen && 'screen', c.input && 'mouse and keyboard'].filter(Boolean).join(', ');
++        const desks = c.desks ? `<span class="muted">${esc(deskWords(c.desks))}</span>` : '';
          const waiting = Number.isInteger(m.computer_waiting) && m.computer_waiting > 0
              ? ` <span class="pill warn">${m.computer_waiting} waiting for you on the machine</span>` : '';
--        return `<div class="machine-computer"><span class="pill">Computer: ${esc(c.level ? LEVELS[c.level] : 'on')}</span><span class="muted">${esc(can)}</span>${waiting}`
++        return `<div class="machine-computer"><span class="pill">Computer: ${esc(c.level ? LEVELS[c.level] : 'on')}</span><span class="muted">${esc(can)}</span>${desks}${waiting}`
              + `<form method="post" action="/machines/${esc(m.id)}/agent-computer"><input type="hidden" name="on" value="${m.agent_computer ? '0' : '1'}">`
              + `<button type="submit" class="button quiet" aria-pressed="${m.agent_computer ? 'true' : 'false'}">${m.agent_computer ? 'Stop my agent using this computer' : 'Let my agent use this computer'}</button></form>`
              + (c.screenStream && m.online ? `<form method="post" action="/machines/${esc(m.id)}/screen"><button type="submit" class="button quiet">${m.computer_screen_stream === 'live' ? 'Watch my screen' : 'Show my screen'}</button></form>` : '')
@@@ -763,6 +774,9 @@ function renderMachinesPage({ machines = [], pairing = null }) {
  <li class="card"><h2>Or let your agents use this computer</h2>
  <pre tabindex="0" class="installer"><code>${esc(pairing.installer.replace(/ --worker$/, ' --computer ask'))}</code></pre>
  <p class="muted">Instead of running jobs, the machine's terminal, files and screen become usable by your agents, at the level you set on the machine: <code>ask</code> waits for <code>openvibe-node approve</code> there before anything runs or changes. The Node runs as your own account, never root. <a href="https://github.com/OpenVibers/OpenVibe.Node/blob/main/docs/computer.md">How it works</a>.</p></li>
++<li class="card"><h2>Or make a spare computer a desk host</h2>
++<pre tabindex="0" class="installer"><code>${esc(pairing.installer.replace(/ --worker$/, ' --desk-host'))}</code></pre>
++<p class="muted">An old laptop, a mini PC or a spare workstation becomes a place where your agents work: each task gets a desk of its own, with its own browser, and you can watch any desk and take it over. No screen, keyboard or sign-in needed on it. It runs as its own account and only for your agents; the installer adds what desks need and sizes them to its memory. Linux. <a href="https://github.com/OpenVibers/OpenVibe.Node/blob/main/docs/computer.md#desk-hosts---desk-host-node-v0200">How it works</a>.</p></li>
  <li class="card"><h2>Or enter the pairing code</h2><p><strong class="code">${esc(pairing.code)}</strong></p>
  <p class="muted">Valid until <time datetime="${esc(pairing.expires_at)}">${esc(pairing.expires_at)}</time>. It works once.</p></li></ol>
  <p class="muted">Reload this page once the installer says it is paired: the machine shows up above.</p>`
ddiff --git a/test/machine-computer.test.js b/test/machine-computer.test.js
iindex e31abe0..1a7f77b 100644
---- a/test/machine-computer.test.js
++++ b/test/machine-computer.test.js
@@@ -320,6 +320,25 @@ const { boot, check, done } = require('./helpers/app');
          assert.strictEqual((await t.db.maybe('SELECT agent_computer FROM devices WHERE id = $1', [mine.deviceId])).agent_computer, false);
      });
  
++    await check('the machines page says what desks each machine runs, and offers to make a spare computer a desk host', async () => {
++        const cookie = (user) => ({ Cookie: `ov_token=${t.network.signUser(user)}` });
++        const desk = { level: 'trusted', window_manager: 'openbox', input: true, screen: true, named: true };
++        const host = await machine(alex, { files: COMPUTER.files, desk: { ...desk, max_desks: 4, kinds: ['desktop', 'browser'], profiles: true } });
++        const mac = await machine(alex, { ...COMPUTER, desk: { ...desk, window_manager: null, max_desks: 2, kinds: ['browser'] } });
++        const html = await (await fetch(`${t.base}/machines`, { headers: cookie(alex) })).text();
++        assert.ok(html.includes('Desks for your agents: 4 at once, or twice as many browser desks, sign-ins kept'), 'a desk host');
++        assert.ok(html.includes('Desks for your agents: 4 browser desks at once'), 'a Mac: browser desks only');
++        const add = await fetch(`${t.base}/machines`, { method: 'POST', redirect: 'manual', body: '', headers: { 'Content-Type': 'application/x-www-form-urlencoded', ...cookie(alex) } });
++        assert.strictEqual(add.status, 201);
++        const page = await add.text();
++        assert.ok(page.includes('Or make a spare computer a desk host'));
++        const hostCmd = /<code>(curl -fsSL [^<]+ --desk-host)<\/code>/.exec(page);
++        assert.ok(hostCmd, 'the desk host install command');
++        assert.ok(!hostCmd[1].includes('--worker'), 'a desk host never runs the job worker too');
++        host.c.close();
++        mac.c.close();
++    });
++
      await check('Watch sends only probes, only where the owner let their watches use the computer', async () => {
          const watch = t.network.signService({ sub: 'svc:watch', cap: ['bot.computer.control'] });
          const asWatch = { token: watch, headers: { 'X-OV-Subject': alex.subject } };