fix: session panel wider + two-line layout for session names

Root cause: 300px panel minus edit btn (28px) + meta (~130px) + delete
btn (28px) + gaps/padding left only ~70px (~7 chars) for the session name.

- Panel: 300px → 420px desktop, 300px → 380px mobile drawer
- Max-height: 340px → 400px
- Session item: name and meta now in a .session-body flex column, so the
  name gets full body width (panel minus two buttons) — meta lives below
- Edit mode: hides .session-body + delete, input takes the full body slot

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

cortex/static/app.js

@@ -516,23 +516,27 @@
                 editBtn.textContent = '✎';
                 editBtn.title = 'Rename session';
 
-                // ── Name label ──────────────────────────────────────────
+                // ── Body: name (top) + meta (below) ─────────────────────
+                const bodyEl = document.createElement('div');
+                bodyEl.className = 'session-body';
+
                 const labelEl = document.createElement('span');
                 labelEl.className = 'session-id';
                 labelEl.textContent = displayName;
 
-                // ── Meta (right of name, before delete) ─────────────────
                 const metaEl = document.createElement('span');
                 metaEl.className = 'session-meta';
                 metaEl.textContent = `${s.message_count} msgs · ${timeAgo(s.updated)}`;
 
+                bodyEl.append(labelEl, metaEl);
+
                 // ── Delete button (far right) ────────────────────────────
                 const delBtn = document.createElement('button');
                 delBtn.className = 'session-delete-btn';
-                delBtn.textContent = '×';
                 delBtn.title = 'Delete session';
+                delBtn.textContent = '×';
 
-                item.append(editBtn, labelEl, metaEl, delBtn);
+                item.append(editBtn, bodyEl, delBtn);
 
                 // Click anywhere on the row (not a button) → resume
                 item.addEventListener('click', (e) => {
@@ -548,9 +552,8 @@
                     input.value = s.name || '';
                     input.placeholder = s.session_id;
 
-                    // Hide name, meta, delete — input takes their space
-                    labelEl.hidden = true;
-                    metaEl.hidden = true;
+                    // Swap body + delete for the input
+                    bodyEl.hidden = true;
                     delBtn.hidden = true;
 
                     editBtn.textContent = '✓';
@@ -578,8 +581,7 @@
 
                     function cancelEdit() {
                         input.remove();
-                        labelEl.hidden = false;
-                        metaEl.hidden = false;
+                        bodyEl.hidden = false;
                         delBtn.hidden = false;
                         editBtn.textContent = '✎';
                         editBtn.title = 'Rename session';