Function cachedRequest

Wraps an Octokit repos.get-style call with ETag caching and request deduplication.

Usage:

const data = await cachedRequest(cache, octokit, '/repos/owner/repo', () =>
  octokit.repos.get({ owner, repo: name }),
);
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1. If an identical request is already in-flight, returns the existing promise (request deduplication).
2. If a cached ETag exists, sends If-None-Match. On 304, returns the cached body without consuming a rate-limit point.
3. On a fresh 200, caches the ETag + body for next time.