fix: show session friendly name in resume message and status bar

/history/{session_id} now returns a 'name' field alongside messages.
resumeSession() uses data.name first, then the sessionNames map, then
raw ID as fallback — so named sessions display correctly even on page
load before the sessions panel has been opened.

'Resumed session X' message also now shows the friendly name.

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

cortex/static/app.js

@@ -642,9 +642,13 @@
             if (!res.ok) throw new Error(`HTTP ${res.status}`);
             const data = await res.json();
 
+            // Prefer name from API response, fall back to sessionNames map, then raw ID
+            const displayName = data.name || sessionNames.get(id) || id;
+            sessionNames.set(id, displayName);
+
             messagesEl.innerHTML = '';
             sessionId = id;
-            sessionEl.textContent = `session: ${sessionNames.get(id) || id}`;
+            sessionEl.textContent = `session: ${displayName}`;
             currentHistory = [];
 
             for (let i = 0; i < data.messages.length; i++) {
@@ -662,7 +666,7 @@
                 }
             }
 
-            if (!silent) addMessage('system', `Resumed session ${id}`);
+            if (!silent) addMessage('system', `Resumed session: ${displayName}`);
             scrollToBottom();
             sessionsPanel.classList.remove('open');
             sessionsBackdrop.classList.remove('open');