parsing nested api responses — without crashing on a missing key

Last drill of the chapter. Write a function summarize_search(response) that takes a GitHub-shaped search response and returns a list of strings, one per repo, in this format:

<name> (★<stars>) — <owner>

Walk the response defensively:

• If items is missing or empty, return [].
• For each repo, default name to "<unnamed>", stargazers_count to 0, and the owner's login to "<unknown>".

The starter has a response with two complete repos and one repo missing its owner. Use the bottom loop as-is.

Expected output:

fastapi (★70000) — tiangolo
httpx (★12000) — encode
mystery-repo (★5) — <unknown>