Void xbps "failed to download signature": stale mirror, switch to repo-fastly

If xbps-install fails with failed to download '<pkg>' signature from <mirror>: Not Found, the mirror's repodata lists a package version whose .xbps and .sig2 files it hasn't synced yet. Check with curl -I <mirror>/current/<pkg>-<ver>.x86_64.xbps.sig2 across mirrors: repo-fastly.voidlinux.org (the official CDN) had it while repo-default and a third-party mirror both returned 404. Fix: write repository=https://repo-fastly.voidlinux.org/current to /etc/xbps.d/00-repository-main.conf (it overrides /usr/share/xbps.d), run xbps-install -S, then retry.