dunn.dev/pipeline 4.6.0

`ci-runtime-go` now builds on UBI10 (`ubi10/ubi:10.2` builder,
`ubi10/ubi-micro:10.2` final), completing the estate's UBI10 train:
consumers pin this catalog at fixed tags, so this release is what
actually moves them off ubi9. A **minor**: no template input added,
removed, or renamed.

- **`ci-runtime-go`: base moved ubi9 → ubi10.** Builder `ubi10/ubi:10.2`,
  final `ubi10/ubi-micro:10.2`; the OCI `base.name` label now names the
  real base (!211). Zero ubi9 references remain in any Containerfile.
- **`renovate-config.json`: UBI9→UBI10 `replacement` rules added; the
  cairn `platformAutomerge: false` interim override removed** (!240) —
  its premise died twice: the branch-head starvation was fixed in the
  cairn repos themselves, and Renovate's own merge `PUT` cannot satisfy
  this estate's sha-required merges.
- Routine tracking: golang 1.26, `buildah:stable`, renovate 44,
  `anchore/syft`, ubi10 digests.

- **`signal-digest`: `_request()` retries transient read timeouts**
  (3 attempts, short backoff; !251) — a single slow gitlab.com answer no
  longer kills the digest job. Real HTTP status answers propagate
  unchanged.