feat: last-used persona cookie, emoji dropdown, theme support, auth status move

- cx_last_persona cookie set on serve_ui; root/login/help/settings
  redirects use preferred persona from cookie instead of alphabetically first
- /api/personas returns [{name, emoji}] objects; persona switcher dropdown
  renders emoji + name with flex layout and .pd-emoji span
- Help, Settings, Model Registry pages apply localStorage theme on load
  (no flash); CSS variables for dark/light replacing all hardcoded hex values
- Claude CLI auth status moved from prominent chat banner to Anthropic
  provider block in Model Registry — live dot indicator (ok/warn/err)
- Auth banner removed from main chat UI (index.html, app.js, style.css)
- Add Model collapsed into Models section as <details> to shorten page
- Light-mode overrides for provider icons, model badges, ctx-badge, tags
  (Anthropic/Google/local colors now readable in both themes)
- Help page gains table, pre/code, hr styles for HELP.md rendered content

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/static/app.js

@@ -360,10 +360,18 @@
                 personaDropEl.innerHTML = '';
 
                 personas.forEach(p => {
+                    const name  = p.name  || p;
+                    const emoji = p.emoji || '✨';
                     const a = document.createElement('a');
-                    a.href = `/${CORTEX_USER}/${p}`;
-                    a.textContent = p.charAt(0).toUpperCase() + p.slice(1);
-                    if (p === CORTEX_PERSONA) a.classList.add('active');
+                    a.href = `/${CORTEX_USER}/${name}`;
+                    if (name === CORTEX_PERSONA) a.classList.add('active');
+                    const emojiEl = document.createElement('span');
+                    emojiEl.className = 'pd-emoji';
+                    emojiEl.textContent = emoji;
+                    a.appendChild(emojiEl);
+                    const nameEl = document.createElement('span');
+                    nameEl.textContent = name.charAt(0).toUpperCase() + name.slice(1);
+                    a.appendChild(nameEl);
                     personaDropEl.appendChild(a);
                 });
 
@@ -1493,19 +1501,6 @@
             try { data = JSON.parse(e.data); } catch { return; }
             if (data.type === 'keepalive') return;
 
-            if (data.type === 'claude_auth_expired') {
-                let banner = document.getElementById('claude-auth-banner');
-                if (!banner) {
-                    banner = document.createElement('div');
-                    banner.id = 'claude-auth-banner';
-                    banner.style.cssText = 'position:fixed;top:0;left:0;right:0;z-index:9999;background:#7c2d12;color:#fef2f2;padding:0.6rem 1rem;font-size:0.85rem;display:flex;align-items:center;justify-content:space-between;gap:1rem;';
-                    banner.innerHTML = '<span>⚠️ Claude authentication expired — run <code style="background:#991b1b;padding:0.1rem 0.3rem;border-radius:3px;">claude</code> in your terminal to re-authenticate, then reload.</span>'
-                        + '<button onclick="this.parentElement.remove()" style="background:none;border:none;color:#fef2f2;font-size:1.1rem;cursor:pointer;padding:0 0.3rem;">✕</button>';
-                    document.body.prepend(banner);
-                }
-                return;
-            }
-
             if (data.type !== 'nct_message' && data.type !== 'nct_response') return;
 
             if (sessionId === data.session_id) {
@@ -1704,57 +1699,6 @@
         syncHeight();
         addMessage('system', 'Session started');
 
-        // ── Auth token warning banner ─────────────────────────────
-        const authBanner      = document.getElementById('auth-banner');
-        const authBannerMsg   = document.getElementById('auth-banner-msg');
-        const authBannerHint  = document.getElementById('auth-banner-hint');
-        const authBannerClose = document.getElementById('auth-banner-close');
-
-        async function checkAuthStatus() {
-            try {
-                const res = await fetch('/auth/status');
-                if (!res.ok) return;
-                const d = await res.json();
-
-                const warnings = [];
-                const fixes    = [];
-                let anyExpired = false;
-
-                if (d.claude?.warning) {
-                    if (d.claude.expired) {
-                        warnings.push('✕ Claude CLI token has expired');
-                        anyExpired = true;
-                    } else {
-                        warnings.push(`⚠ Claude CLI token expires in ${d.claude.access_token_hours_remaining}h`);
-                    }
-                    fixes.push('<code>claude</code>');
-                }
-
-                if (d.gemini?.warning) {
-                    warnings.push('⚠ Gemini CLI not authenticated');
-                    fixes.push('<code>gemini</code>');
-                }
-
-                if (!warnings.length) {
-                    authBanner.classList.remove('show');
-                    return;
-                }
-
-                authBannerMsg.innerHTML = warnings.join('<br>');
-                authBannerHint.innerHTML =
-                    `To fix: SSH into the Cortex host and run ${fixes.join(' and/or ')} — `
-                    + 'follow the login prompt, then restart Cortex.';
-                authBanner.classList.toggle('expired', anyExpired);
-                authBanner.classList.add('show');
-            } catch { /* silently ignore — don't break the UI */ }
-        }
-
-        authBannerClose.addEventListener('click', () => authBanner.classList.remove('show'));
-
-        checkAuthStatus();
-        // Re-check every 30 minutes
-        setInterval(checkAuthStatus, 30 * 60 * 1000);
-
         // ── Initial render ────────────────────────────────────────────
         // Process all static Lucide SVGs in the header + stop button,
         // and seed the mode UI (which also calls render_icons internally).