Merge pull request 'fix(digest): digest 暂存改 mktemp（PLAT-014 二段，v5 前置）' (#3) from task/PLAT-014-digest-mktemp into main

run 924 build 红根因：容器 install chown -R node:node workspace → 宿主 digest 步
mkdir -p .tmp-ci EACCES（897 时代 runner 为 root 故绿；治理后必红）。
修法：digest/manifest 暂存文件改宿主 mktemp 目录（runner 自建 tmp 可写），
两处 digest 步（verify/script 路径）同修。合并后打 v5。

.gitea/workflows/reusable/oci-build-push-verify.yml

@@ -193,8 +193,11 @@ jobs:
           set -eu
           IMAGE_TAG="git-${GITHUB_SHA}"
           printf '%s' "${GITHUB_SHA}" | grep -Eq '^[0-9a-f]{40}$'
-          mkdir -p .tmp-ci
-          digest_file=".tmp-ci/digests.txt"
+          # PLAT-014: the containerized install chowns the workspace to the
+          # helper's node user, so a host-side mkdir in $PWD fails with EACCES
+          # on the non-root runner. Keep host-written scratch in mktemp space.
+          digest_dir="$(mktemp -d)"
+          digest_file="$digest_dir/digests.txt"
           : >"$digest_file"
           cache_args=""
           if [ -n "${CACHE_REGISTRY_REF}" ]; then
@@ -248,7 +251,7 @@ jobs:
               --provenance=mode=max \
               --sbom=true \
               --push .
-            manifest_file=".tmp-ci/index-${service}.json"
+            manifest_file="${digest_dir}/index-${service}.json"
             docker buildx imagetools inspect "${image}" --raw >"$manifest_file"
             if [ -n "${VERIFY_COMMAND}" ]; then
               # VERIFY_COMMAND carries its own interpreter (e.g. "node x.mjs"
@@ -284,8 +287,8 @@ jobs:
         run: |
           set -eu
           image_tag="git-${GITHUB_SHA}"
-          digest_file=".tmp-ci/digests-script.txt"
-          mkdir -p .tmp-ci
+          digest_dir="$(mktemp -d)"
+          digest_file="${digest_dir}/digests-script.txt"
           : >"$digest_file"
           while IFS='|' read -r service dockerfile target; do
             [ -n "${service:-}" ] || continue