wip(web): agent preset UI flow — creator intro, custom group, subagent flash, chrome polish

packages/client/ui-sidebar/src/client/SidebarRoot.module.css

@@ -84,7 +84,7 @@
   gap: 8px;
   height: 60px;
   padding: 8px 0 8px 4px;
-  margin-bottom: 16px;
+  margin-bottom: 8px;
   box-sizing: border-box;
   overflow: hidden;
 }
@@ -157,8 +157,8 @@
   color: var(--dsw-alias-label-primary);
 }
 
-/* New Session: 38px capsule (figma 133:7634); collapsed it renders as the
-   rail's plain icon control. */
+/* New Session: 38px bar, 12px radius (figma 133:7634 geometry, squared-off
+   corners); collapsed it renders as the rail's plain icon control. */
 .newSession {
   flex: none;
   display: flex;
@@ -170,7 +170,7 @@
   margin: 0 2px 20px; /* bottom: former headerBlock padBottom 12 + root gap 8 */
   box-sizing: border-box;
   border: 1px solid var(--dsw-alias-border-l2);
-  border-radius: 24px;
+  border-radius: 12px;
   background: var(--dsw-alias-button-elevated-fill);
   color: var(--dsw-alias-label-primary);
   font-size: 14px;