fix(ui): activate FleetView before nested roster assertion

After #164 nested records are filtered from the coordinator fleet, but
#169 keeps the roster collapsed until selection is active. Press ↓ first
so the nested-hide assertion observes the visible list.

Author: xz-dev

test/fleet-list.test.ts

@@ -166,6 +166,8 @@ describe("FleetList navigation", () => {
       makeRecord({ id: "top", description: "top-level" }),
       makeRecord({ id: "nested", description: "nested-child", parentAgentId: "top" }),
     ]);
+    // Roster stays collapsed until selection is active (#169).
+    h.press(DOWN);
     const output = h.render().join("\n");
     expect(output).toContain("top-level");
     expect(output).not.toContain("nested-child");