guest-kernel pin: follow ossein-kernel's move to vX.Y.Z.N release tags #223

farcloser/ossein-kernel moves its release tag from X.Y.Z-ossein.N to limen's rebuild tag vX.Y.Z.N (farcloser/ossein-kernel#194, limen's book/forks.md). The guest-kernel entry in pins.yaml reads the kernel's GitHub releases with a versioning written for the old shape:

versioning: regex:^(?<major>\d+)\.(?<minor>\d+)\.(?<patch>\d+)-ossein\.(?<build>\d+)$
version: 7.2.9-ossein.1

A vX.Y.Z.N tag does not parse under it, so Renovate will not propose the first release under the new shape, and the pin would stay on 7.2.9-ossein.1 silently.

On the first kernel release tagged vX.Y.Z.N:

• move version and digest.version to that tag, and digest.sha256 to the kernel's line in its SHA256SUMS (after cosign has verified the manifest, as the entry's comment says);
• replace the entry's versioning with the shared one. limen's canonical Renovate configuration (.limen/renovate.json, from the limen release that carries A fork's rebuild tag (vX.Y.Z.N) releases through goreleaser, is proposed by Renovate and pins a registry limen#635) gives every v-prefixed farcloser pin read by the regex managers a regex: versioning that compares the fourth segment, so the entry needs none of its own once that configuration has reached this repository; until then, regex:^v(?<major>\d+)\.(?<minor>\d+)\.(?<patch>\d+)\.(?<build>\d+)$.

The URL templates (releases/download/${version}/…) take the v-prefixed tag as they are. Published releases keep their old tags.