isFineGrainedGitHubPat function
Whether token is a GitHub fine-grained PAT (v2, github_pat_…).
Per the official Copilot CLI docs this IS a supported Copilot
credential — but only with the "Copilot Requests" permission, so the
connect flow uses this to print an informational hint at paste time
(the exchange itself decides).
Implementation
bool isFineGrainedGitHubPat(String token) => token.startsWith('github_pat_');