refactor(dashboard): change SpawnModal from overlay modal to dropdown

Position the spawn modal directly under the 'New Agent' button without a
blur overlay. Uses click-outside dismissal and absolute positioning.
Reduces visual disruption for quick agent spawning.

dashboard/components/Modal.js

@@ -18,10 +18,12 @@ export function Modal({ session, conversations, onClose, onRespond, onFetchConve
       return;
     }
 
+    let stale = false;
     const agent = session.agent || 'claude';
     fetchSkills(agent)
-      .then(config => setAutocompleteConfig(config))
-      .catch(() => setAutocompleteConfig(null));
+      .then(config => { if (!stale) setAutocompleteConfig(config); })
+      .catch(() => { if (!stale) setAutocompleteConfig(null); });
+    return () => { stale = true; };
   }, [session?.agent]);
 
   // Animated close handler