Fix NoneType error in render script for null GitHub pinned item nodes

[Copilot]

The scripts/render script crashes with TypeError: 'NoneType' object is not subscriptable when the GitHub GraphQL API returns edges with null nodes (e.g., deleted/private pinned repos).

• Filter null nodes: Skip edges where node is None before iterating over pinned repos
• Guard null fields: Handle None description fields in format_repo by defaulting to empty string, since GitHub repos can have no description set

# Before
repos = repos["data"]["user"]["pinnedItems"]["edges"]

# After
repos = [
    r
    for r in repos["data"]["user"]["pinnedItems"]["edges"]
    if r.get("node") is not None
]

[dfm]

@copilot Which repo is causing the issue?

[Copilot]

@copilot Which repo is causing the issue?

I can't determine the exact repo from the available data. The committed data/repos.json is stale — it contains all 6 valid nodes. The null node only appeared in the freshly fetched data during the CI run (when scripts/update-github-repos calls the GraphQL API), and that data wasn't persisted.

The most likely cause: the GraphQL query uses ... on Repository inline fragment inside pinnedItems. If a pinned item references a repo that was deleted, transferred, or made private/inaccessible to the API token, the API returns "node": null for that edge. The repos owned by other orgs (jax-ml/jax, exoplanet-dev/exoplanet, daft-dev/daft) would be the most likely candidates if access changed.

You could check by running the GraphQL query manually with your token to see which edge currently returns null.