Admin: single AI viewers engine

ddiff --git a/public/admin.html b/public/admin.html
iindex 284e855e..36047db4 100644
---- a/public/admin.html
++++ b/public/admin.html
@@@ -1689,7 +1689,7 @@ const AI_KEYS = ['ai_enabled', 'ai_provider', 'ai_api_key', 'ai_base_url', 'ai_m
      'ai_model_chat', 'ai_model_vision', 'ai_model_director', 'ai_model_summary',
      'ai_paste_analysis_enabled', 'ai_stream_memory_enabled', 'ai_stream_capture_interval_sec', 'ai_transcription_enabled', 'ai_timeline_enabled',
      'ai_max_cost_usd_per_day', 'ai_input_cost_per_mtok', 'ai_output_cost_per_mtok', 'ai_pricing_json',
--    'ai_viewers_enabled', 'ai_viewers_engine', 'ai_viewers_max_roster', 'ai_viewers_max_lines_per_min', 'ai_viewers_global_cap_usd_per_day', 'ai_viewers_default_settings_json'];
++    'ai_viewers_enabled', 'ai_viewers_max_roster', 'ai_viewers_max_lines_per_min', 'ai_viewers_global_cap_usd_per_day', 'ai_viewers_default_settings_json'];
  
  async function loadAi() {
      const c = document.getElementById('ai-content');
@@@ -1794,14 +1794,14 @@ async function loadAiViewersFleet() {
                  <span>Default engine: <b>${esc(d.engine_default)}</b></span>
                  <span>Kill switch: <b style="color:${d.kill_switch ? '#f87171' : '#4ade80'}">${d.kill_switch ? 'ENGAGED (all channels silent)' : 'off'}</b></span>
                  <span>Shared-key viewer spend today: <b>${money(d.global_spend_today_usd)}</b></span>
--                <span class="muted" style="font-size:12px">Change ai_viewers_enabled / ai_viewers_engine in Configuration below.</span>
++                <span class="muted" style="font-size:12px">The kill switch is ai_viewers_enabled in Configuration below.</span>
              </div>
              ${d.running.length ? `<table style="width:100%;font-size:13px;border-collapse:collapse;margin-bottom:10px"><tr><th style="text-align:left">Running now</th><th>Engine</th><th>Stream</th><th>Bots</th><th>Mode</th><th>Lines</th><th>Passes</th><th style="text-align:right">Cost</th><th></th></tr>
                  ${d.running.map(r=>`<tr><td>${esc(r.username||('#'+r.user_id))}</td><td>${esc(r.engine)}</td><td>${r.stream_id}</td><td>${r.bots}</td><td>${esc(r.paused ? 'paused' : (r.mode||''))}</td><td>${r.stats ? r.stats.lines : '—'}</td><td>${r.stats ? r.stats.ticks : '—'}</td><td style="text-align:right">${r.stats ? money(r.stats.cost) : '—'}</td>
                      <td style="white-space:nowrap"><button class="btn btn-sm btn-outline" onclick="aiViewersAdmin(${r.user_id},'${r.paused ? 'resume' : 'pause'}')">${r.paused ? 'Resume' : 'Pause'}</button> <button class="btn btn-sm btn-danger" onclick="aiViewersAdmin(${r.user_id},'stop')">Stop + disable</button></td></tr>`).join('')}</table>` : '<p class="muted" style="margin:0 0 8px">No AI viewer workers running right now.</p>'}
              <details><summary class="muted" style="cursor:pointer;font-size:12px">Channels with AI viewers configured (${d.channels.length})</summary>
--            <table style="width:100%;font-size:13px;border-collapse:collapse"><tr><th style="text-align:left">Channel</th><th>Enabled</th><th>Engine</th><th>Activity</th><th>Bots</th><th>Key</th><th style="text-align:right">Today / cap</th></tr>
--                ${d.channels.map(c=>`<tr><td>${esc(c.username)}</td><td>${c.enabled ? '✔' : '—'}</td><td>${esc(c.engine||'default')}</td><td>${esc(c.activity||'—')}</td><td>${c.bots}</td><td>${c.shared_key ? 'shared' : 'BYO'}</td><td style="text-align:right">${money(c.spent_today_usd)} / ${c.shared_key ? '$'+c.cap_usd.toFixed(2) : '∞'}</td></tr>`).join('')}</table></details>`;
++            <table style="width:100%;font-size:13px;border-collapse:collapse"><tr><th style="text-align:left">Channel</th><th>Enabled</th><th>Activity</th><th>Bots</th><th>Key</th><th style="text-align:right">Today / cap</th></tr>
++                ${d.channels.map(c=>`<tr><td>${esc(c.username)}</td><td>${c.enabled ? '✔' : '—'}</td><td>${esc(c.activity||'—')}</td><td>${c.bots}</td><td>${c.shared_key ? 'shared' : 'BYO'}</td><td style="text-align:right">${money(c.spent_today_usd)} / ${c.shared_key ? '$'+c.cap_usd.toFixed(2) : '∞'}</td></tr>`).join('')}</table></details>`;
      } catch (e) { el.innerHTML = `<span class="muted">Unavailable: ${esc(e.message)}</span>`; }
  }
  async function aiViewersAdmin(userId, action) {