Fetch only needed fields from GitHub contributors API — `id` (numeric user ID) collected but only `login` and `html_url` are displayed

[ooloth]

Why

The contributors GraphQL query fetches the GitHub numeric user id and uses it as a React list key, but login alone would serve as a stable unique key — unnecessarily collecting a persistent cross-site identifier.

Current state

src/queries/useContributorsData.ts lines 17–18 fetch id in the GraphQL query. src/components/Contributors.tsx line 47 uses contributor.id as the React key. The rendered UI displays only the avatar image and a link — neither of which requires the numeric id. The login string is a stable, human-readable unique identifier that could serve as the list key.

Ideal state

• The query does not fetch the numeric id field.
• login (or html_url) is used as the React list key.
• The numeric GitHub user ID is not fetched, stored in the Gatsby data layer, or used anywhere in the component tree.

Out of scope

• Removing id from the upstream GitHub API response (it is returned by default; the fix is to not fetch it in the query).

Starting points

• src/queries/useContributorsData.ts — the GraphQL query: remove the id field selection.
• src/components/Contributors.tsx — line 47: replace key={contributor.id} with key={contributor.login}.

QA plan

1. Remove id from the GraphQL query and update the React key to use login.
2. Run gatsby build — expect no TypeScript errors.
3. Open the built site and confirm the Contributors section renders all contributors correctly.
4. Inspect the Gatsby data layer — confirm no id field exists on contributor nodes.

Done when

The contributors query does not fetch the numeric GitHub id, and login is used as the React list key.