ci(promote-base-latest): re-point base-latest by digest, not need_build

The gate keyed off need_build=='true', assuming need_build==false meant
base-latest was already current. A dry-run dispatch (promote_latest=false)
that pre-builds base-<hash> falsifies that: the later tag run sees
need_build==false and skipped promotion, leaving base-latest one base
behind (observed 2026-06-27, v1.2.3 dry-run-first release).

Gate now runs on every tag release / promote dispatch; the no-op
optimization moved into the step as a crane digest compare so it re-tags
only when base-latest actually differs from the released base-<hash>.
Workflow-only change; base hash unaffected (no base rebuild).

.gitea/workflows/docker-publish.yml

@@ -565,16 +565,19 @@ jobs:
     needs:
       - base-decide
       - build-variant
-    # Skip on cache-hit base builds: when need_build=false, base-latest
-    # already points at the same digest as base-<hash>, so the retag is
-    # a tautology and any transient failure of it is purely cosmetic.
-    # Manual workflow_dispatch with promote_latest=true overrides this
-    # gate as an escape hatch (e.g., if base-latest got hand-deleted).
+    # Run on every tag release (and on promote_latest=true dispatches).
+    # The job-level gate deliberately does NOT key off need_build anymore:
+    # the actual no-op optimization moved INTO the step as a digest compare
+    # (see below). Keying the gate on need_build was wrong because a prior
+    # dry-run dispatch (promote_latest=false) can pre-build+push base-<hash>,
+    # making need_build=false on the subsequent tag run even though
+    # base-latest is still stale — the old gate then skipped promotion and
+    # left base-latest pointing at the PREVIOUS base. (Observed 2026-06-27,
+    # v1.2.3: dry-run-first release left base-latest one base behind.)
     if: |
       always() &&
       needs.build-variant.result == 'success' &&
-      (inputs.promote_latest == 'true' ||
-       (github.ref_type == 'tag' && needs.base-decide.outputs.need_build == 'true'))
+      (inputs.promote_latest == 'true' || github.ref_type == 'tag')
     runs-on: ubuntu-latest
     container:
       image: catthehacker/ubuntu:act-latest
@@ -596,11 +599,31 @@ jobs:
           crane auth login docker.io \
             -u ${{ vars.DOCKERHUB_USERNAME }} \
             -p "${{ secrets.DOCKERHUB_TOKEN }}"
-      - name: Re-tag base-<hash> as base-latest
+      - name: Re-tag base-<hash> as base-latest (only if stale)
+        env:
+          BASE_HASH_REF: ${{ env.IMAGE }}:${{ needs.base-decide.outputs.base_tag }}
+          BASE_LATEST_REF: ${{ env.IMAGE }}:base-latest
         run: |
-          crane copy \
-            ${{ env.IMAGE }}:${{ needs.base-decide.outputs.base_tag }} \
-            ${{ env.IMAGE }}:base-latest
+          set -euo pipefail
+          # Correctness invariant: after a release, base-latest must resolve to
+          # the SAME digest as the base-<hash> the just-built variants were
+          # FROM. Compare digests rather than trusting need_build — a prior
+          # dry-run dispatch can pre-build base-<hash>, so need_build=false on
+          # the tag run does NOT imply base-latest is already current. When the
+          # digests already match (genuine cache-hit release) this is a no-op,
+          # so we skip the crane copy entirely — preserving the original
+          # "don't do a tautological retag" intent and avoiding any cosmetic
+          # transient-failure exposure on releases that change nothing.
+          want=$(crane digest "${BASE_HASH_REF}")
+          have=$(crane digest "${BASE_LATEST_REF}" 2>/dev/null || echo "")
+          echo "base-<hash> digest: ${want}"
+          echo "base-latest digest: ${have:-<absent>}"
+          if [ "${want}" = "${have}" ]; then
+            echo "base-latest already current; nothing to promote."
+          else
+            echo "Promoting base-latest -> ${BASE_HASH_REF}"
+            crane copy "${BASE_HASH_REF}" "${BASE_LATEST_REF}"
+          fi
 
   # ── Phase 6: update Hub description (only on real release runs) ────
   update-description: