test(showcase): strands-python uses showcase shell, set hasAppMode true

starter-smoke @interaction branches on `starter.hasAppMode`: when true it
clicks the App/Chat toggle and asserts the canvas + textarea; when false
it assumes a CopilotSidebar layout and asserts "Popup Assistant".

Strands now renders the same showcase shell as langgraph-python (App/Chat
toggle + ExampleCanvas), so the smoke test must take the `hasAppMode:
true` branch. Without this flag the test waits for "Popup Assistant" text
that never appears and times out.