fix: session delete button always visible, session name truncates properly

- Remove opacity:0/hover-reveal on session × — always shown in the panel
- session-id: flex:1 + text-overflow:ellipsis prevents overflow pushing × offscreen
- min-width on delete btn ensures tap target is always reachable

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

cortex/static/style.css

@@ -182,21 +182,25 @@
             color: var(--muted);
             font-size: 1.1rem;
             line-height: 1;
-            padding: 2px 4px;
+            padding: 2px 6px;
             cursor: pointer;
             border-radius: 3px;
             flex-shrink: 0;
-            margin-left: 4px;
-            opacity: 0;
-            transition: opacity 0.15s, color 0.15s;
+            transition: color 0.15s;
+            min-width: 28px;
+            text-align: center;
         }
-        .session-item:hover .session-delete-btn { opacity: 1; }
         .session-delete-btn:hover { color: #e06c75; }
 
         .session-id {
             font-family: monospace;
             font-size: 0.85rem;
             color: var(--text);
+            flex: 1;
+            min-width: 0;
+            overflow: hidden;
+            text-overflow: ellipsis;
+            white-space: nowrap;
         }
 
         .session-meta {
@@ -1061,7 +1065,6 @@
             }
 
             .session-delete-btn {
-                opacity: 1;
                 font-size: 1.3rem;
                 padding: 4px 8px;
                 min-width: 36px;