govulncheck fails on master against the 1.25.12 pin with seven stdlib
advisories, all fixed in 1.25.13: GO-2026-5026, GO-2026-5972, GO-2026-6088,
GO-2026-6089, GO-2026-6090, GO-2026-6091 and GO-2026-6218, across crypto/tls,
encoding/asn1, encoding/xml, html/template, net/http and net/url.
Pinning the next patch would only move the problem to the following advisory,
as it did in 76d0cc2c. setup-go accepts a minor-only spec, so "1.25" resolves
to a patch on that line at run time. Staying on 1.25 rather than "stable"
keeps a move to a new minor a deliberate change, matching the `go 1.25.0`
directive in both go.mod files.
check-latest is required with it: by default setup-go uses the patch already
cached on the runner image, so a minor-only spec alone would keep resolving
to whatever that image ships, currently 1.25.12, and the scan would stay red.