feat: add sidebar session card styles

frontend/style.css

@@ -450,6 +450,79 @@ body {
   border-color: var(--accent);
 }
 
+/* ============================================================
+   Sidebar session card styles
+   ============================================================ */
+
+.sidebar-item {
+  height: 120px;
+  background: var(--bg-secondary);
+  border-bottom: 1px solid var(--border-subtle);
+  cursor: pointer;
+  overflow: hidden;
+  display: flex;
+  flex-direction: column;
+  position: relative;
+}
+
+.sidebar-item:hover {
+  background: var(--bg-surface);
+}
+
+.sidebar-item--active {
+  background: var(--bg-surface);
+  border-left: 3px solid var(--accent);
+}
+
+.sidebar-item-header {
+  display: flex;
+  flex-direction: row;
+  justify-content: space-between;
+  padding: 8px 8px 4px;
+  height: 32px;
+  gap: 4px;
+  align-items: center;
+  flex-shrink: 0;
+}
+
+.sidebar-item-name {
+  font-size: 12px;
+  font-weight: 600;
+  color: var(--text);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  flex: 1;
+  min-width: 0;
+}
+
+.sidebar-item-body {
+  flex: 1;
+  position: relative;
+  overflow: hidden;
+}
+
+.sidebar-item-body pre {
+  position: absolute;
+  bottom: 0;
+  left: 0;
+  right: 0;
+  font-family: 'JetBrains Mono', 'Fira Code', monospace;
+  font-size: 10px;
+  line-height: 1.4;
+  color: var(--text-muted);
+  white-space: pre;
+  padding: 0 8px 6px;
+  margin: 0;
+}
+
+.sidebar-empty {
+  padding: 16px 12px;
+  color: var(--text-muted);
+  font-size: 12px;
+  text-align: center;
+}
+
 .terminal-container {
   flex: 1;
   min-width: 0;