Keep forked chats focused in new tabs (#2038)

* fix(app): focus explicitly opened workspace tabs

Explicit tab navigation could be overwritten by attention-aware workspace
navigation when the visible agent had just finished. Make workspace navigation
own both normal attention selection and explicit targets so callers cannot
sequence them inconsistently.

* test(app): strengthen forked tab focus assertion

packages/app/src/hooks/use-keyboard-shortcuts.ts

@@ -120,7 +120,7 @@ export function useKeyboardShortcuts({
             serverId: action.serverId,
             workspaceId: action.workspaceId,
           };
-          navigateToWorkspace(action.serverId, action.workspaceId);
+          navigateToWorkspace({ serverId: action.serverId, workspaceId: action.workspaceId });
           return true;
         case "navigate-last-workspace":
           return navigateToLastWorkspace();