feat(frontend): Bridge-based UI — auto-load sessions, cascade content display, Bridge send

public/js/session-panel.js

@@ -49,7 +49,7 @@ class SessionPanel {
         <div class="session-indicator ${s.status}"></div>
         <div class="session-info">
           <div class="session-name">${this._escapeHtml(s.name)}</div>
-          <div class="session-detail">${s.host}:${s.cdpPort} · ${this._statusText(s.status)}</div>
+          <div class="session-detail">${s.isBridge ? `${s.stepCount || 0} steps · 대화` : `${s.host}:${s.cdpPort} · ${this._statusText(s.status)}`}</div>
         </div>
         <button class="session-remove" data-remove-id="${s.id}" title="세션 제거">✕</button>
       </div>