merge: reconcile PR 40 with current lab

Integrate lab fff55a78 into PR #40 (cc25d5ba). Lab's modular email
backend/frontend, modular settings, split stylesheets (static/style.css
stays deleted), procfs compatibility, and request-scoped TurnContract
authority win; PR #40's routing classifiers, editor/email/task features,
and style.css changes are ported into lab's module and stylesheet homes.

Integration fixes:
- settings/api.js imports ui.js under its canonical versioned URL
- browser observations keep legacy CAPTCHA/access-block evidence
- artifact turns do not re-trigger broad-web research recovery
- env reference documents PR test-tool variables; page regenerated

PR #40 defects surfaced by lab gates and fixed here:
- web_fetch generic schema drops top-level anyOf (OpenAI contract);
  the compact preview contract still requires url or urls
- get_weather registered as a brokered network read
- new lazy editor modules precached for offline use
- SearXNG pin mirrored into GPU standalone compose files
- image model picker again skips offline endpoints

Tests updated where PR #40 changed behaviour on purpose, and PR tests
moved onto lab's document_source helpers.

static/js/admin.js

@@ -3166,6 +3166,7 @@ function initMcpForm() {
     if (transport === 'stdio' && !command) { msg.textContent = 'Command is required for stdio'; msg.className = 'admin-error'; return; }
     if (transport === 'sse' && !url) { msg.textContent = 'URL is required for SSE'; msg.className = 'admin-error'; return; }
     try { JSON.parse(env); } catch { msg.textContent = 'Env must be valid JSON'; msg.className = 'admin-error'; return; }
+    try { JSON.parse(args); } catch { msg.textContent = 'Args must be valid JSON, e.g. ["-y", "pkg"]'; msg.className = 'admin-error'; return; }
     const fd = new FormData();
     fd.append('name', name); fd.append('transport', transport); fd.append('command', command); fd.append('args', args); fd.append('env', env); fd.append('url', url);
     // If preset has oauthFile config, send credentials for file generation
@@ -3186,6 +3187,10 @@ function initMcpForm() {
     try {
       const res = await fetch('/api/mcp/servers', { method: 'POST', body: fd, credentials: 'same-origin' });
       const data = await res.json();
+      if (!res.ok) {
+        msg.textContent = data.detail || `Failed (${res.status})`; msg.className = 'admin-error';
+        return;
+      }
       if (data.needs_oauth) {
         msg.innerHTML = `Added ${esc(name)} — <a href="/api/mcp/oauth/authorize/${data.id}" target="_blank" style="color:var(--red);font-weight:600;">Authorize with Google</a> to connect`;
         msg.className = 'admin-success';