ci: multi-arch-safe php.net guard and emergency workflow (no platform change)

- scripts/image-label-amd64.sh: index-safe read of the amd64 image's labels
  (OCI index with attestations, Docker manifest list, single manifest).
- scripts/php-emergency-guard.sh: used by both build-push.yaml guard sites;
  same decisions as the old inline step on single-platform images, but FAILS
  CLOSED when the labels cannot be read (only "tag not found" passes).
- lsphp-source-emergency.yaml: push by digest + assemble (copy of HMB
  assemble-multiarch-index.sh); optional arm64; refuses to replace a
  multi-arch production tag with amd64-only unless allow_amd64_only.
- Tests wired into Shell-Checks; main build matrix platforms unchanged.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0185ukXjXyosSkunDsdWz3mb

.gitea/workflows/lsphp-source-emergency.yaml

@@ -15,6 +15,16 @@ run-name: EMERGENCY lsphp php.net build by ${{ gitea.actor }}
 ##
 ## Tags: always  :phpNN-phpnet-X.Y.Z  (immutable, for staging / rollback)
 ##       and     :phpNN               only when push_production_tags = true.
+##
+## Multi-arch safety (docs/arm64/IMAGE-PIPELINE-PLAN.md 2.2 #6, 4.4): each
+## platform is pushed BY DIGEST and the tags are assembled afterwards with
+## scripts/assemble-multiarch-index.sh (copy of haproxy-manager-base's), so a
+## tag is never overwritten with a bare single-platform manifest by accident.
+## arm64 is built from the SAME php.net source in THIS run (continue-on-error);
+## a previous run's arm64 is never re-attached. If a production tag is
+## currently a multi-arch index and arm64 was not built successfully, the
+## production tag is REFUSED unless allow_amd64_only = true (an explicit
+## security-over-parity decision); the immutable tag is still created.
 on:
   workflow_dispatch:
     inputs:
@@ -32,6 +42,16 @@ on:
         required: true
         default: false
         type: boolean
+      build_arm64:
+        description: "Also build linux/arm64 (QEMU, slow, best effort). Needed to keep arm64 in a multi-arch :phpNN."
+        required: false
+        default: false
+        type: boolean
+      allow_amd64_only:
+        description: "Allow replacing a multi-arch production tag with amd64-only when arm64 is not built/failed (ARM hosts then cannot pull it)."
+        required: false
+        default: false
+        type: boolean
 
 jobs:
   Build-lsphp-from-source:
@@ -49,6 +69,8 @@ jobs:
           IN_VERSIONS: ${{ inputs.php_versions }}
           IN_IMAGES: ${{ inputs.images }}
           IN_PROD: ${{ format('{0}', inputs.push_production_tags) }}
+          IN_ARM: ${{ format('{0}', inputs.build_arm64) }}
+          IN_AMD_ONLY: ${{ format('{0}', inputs.allow_amd64_only) }}
           PHPVER: ${{ matrix.phpver }}
           IMG: ${{ matrix.image }}
         run: |
@@ -60,7 +82,11 @@ jobs:
             [[ "$pair" =~ ^(8[2-5])=([0-9]+\.[0-9]+\.[0-9]+)$ ]] || { echo "::error::bad php_versions entry '$pair' (want NN=X.Y.Z, NN in 82..85)"; exit 1; }
             [ "${BASH_REMATCH[1]}" = "$PHPVER" ] && v="${BASH_REMATCH[2]}"
           done
+          case "$IN_ARM" in true|false) ;; *) echo "::error::build_arm64 must be true|false, got '$IN_ARM'"; exit 1 ;; esac
+          case "$IN_AMD_ONLY" in true|false) ;; *) echo "::error::allow_amd64_only must be true|false, got '$IN_AMD_ONLY'"; exit 1 ;; esac
           echo "prod=$IN_PROD" >> "$GITHUB_OUTPUT"
+          echo "arm=$IN_ARM" >> "$GITHUB_OUTPUT"
+          echo "amd_only=$IN_AMD_ONLY" >> "$GITHUB_OUTPUT"
           if [ -z "$v" ] || { [ "$IN_IMAGES" != both ] && [ "$IN_IMAGES" != "$IMG" ]; }; then
             echo "not requested: php${PHPVER} / ${IMG}"; echo "skip=1" >> "$GITHUB_OUTPUT"; exit 0
           fi
@@ -111,6 +137,12 @@ jobs:
         if: steps.t.outputs.skip == '0'
         uses: docker/setup-buildx-action@v3
 
+      - name: Set up QEMU (arm64)
+        if: steps.t.outputs.skip == '0' && steps.t.outputs.arm == 'true'
+        uses: docker/setup-qemu-action@v3
+        with:
+          platforms: arm64
+
       - name: Login to Gitea
         if: steps.t.outputs.skip == '0'
         uses: docker/login-action@v3
@@ -119,13 +151,15 @@ jobs:
           username: ${{ secrets.CI_USER }}
           password: ${{ secrets.CI_TOKEN }}
 
-      - name: Build and push (php.net lsphp)
+      # amd64: required. Pushed untagged by digest; tags are made below.
+      - name: Build amd64 (push by digest)
         if: steps.t.outputs.skip == '0'
+        id: amd64
         uses: docker/build-push-action@v6
         with:
           file: ${{ steps.t.outputs.dockerfile }}
           platforms: linux/amd64
-          push: true
+          outputs: type=image,name=repo.anhonesthost.net/cloud-hosting-platform/${{ steps.t.outputs.image_name }},push-by-digest=true,name-canonical=true,push=true
           build-args: |
             PHPVER=${{ matrix.phpver }}
             OLS_VERSION=1.8.4
@@ -135,7 +169,74 @@ jobs:
             PHP_SRC_VERSION=${{ steps.t.outputs.version }}
             PHP_SRC_SHA256=${{ steps.v.outputs.sha }}
             LSPHP_SOURCE=php.net
-          tags: |
-            repo.anhonesthost.net/cloud-hosting-platform/${{ steps.t.outputs.image_name }}:php${{ matrix.phpver }}-phpnet-${{ steps.t.outputs.version }}
-            ${{ steps.t.outputs.prod == 'true' && format('repo.anhonesthost.net/cloud-hosting-platform/{0}:php{1}', steps.t.outputs.image_name, matrix.phpver) || '' }}
-            ${{ steps.t.outputs.prod == 'true' && matrix.phpver == 85 && format('repo.anhonesthost.net/cloud-hosting-platform/{0}:latest', steps.t.outputs.image_name) || '' }}
+
+      # arm64: best effort, same php.net source and version, never blocks amd64.
+      - name: Build arm64 (push by digest)
+        if: steps.t.outputs.skip == '0' && steps.t.outputs.arm == 'true'
+        id: arm64
+        continue-on-error: true
+        timeout-minutes: 120
+        uses: docker/build-push-action@v6
+        with:
+          file: ${{ steps.t.outputs.dockerfile }}
+          platforms: linux/arm64
+          outputs: type=image,name=repo.anhonesthost.net/cloud-hosting-platform/${{ steps.t.outputs.image_name }},push-by-digest=true,name-canonical=true,push=true
+          build-args: |
+            PHPVER=${{ matrix.phpver }}
+            OLS_VERSION=1.8.4
+            CACHE_BUST=${{ steps.v.outputs.bust }}
+            EXPECT_LSPHP_PKG=${{ steps.v.outputs.pkg }}
+            EXPECT_PHP_VERSION=${{ steps.v.outputs.pkgphp }}
+            PHP_SRC_VERSION=${{ steps.t.outputs.version }}
+            PHP_SRC_SHA256=${{ steps.v.outputs.sha }}
+            LSPHP_SOURCE=php.net
+
+      # Immutable staging/rollback tag: always created (amd64, + arm64 if built).
+      - name: Assemble immutable tag
+        if: steps.t.outputs.skip == '0'
+        env:
+          AMD64_DIGEST: ${{ steps.amd64.outputs.digest }}
+          ARM64_DIGEST: ${{ steps.arm64.outputs.digest }}
+          ARM64_OUTCOME: ${{ steps.arm64.outcome }}
+          REPO: repo.anhonesthost.net/cloud-hosting-platform/${{ steps.t.outputs.image_name }}
+          TAG: php${{ matrix.phpver }}-phpnet-${{ steps.t.outputs.version }}
+        run: |
+          ./scripts/assemble-multiarch-index.sh \
+            --amd64 "$AMD64_DIGEST" \
+            --arm64 "$ARM64_DIGEST" --arm64-outcome "${ARM64_OUTCOME:-skipped}" \
+            --repo "$REPO" --tag "$TAG"
+
+      # Production tags: never silently drop arm64 from a multi-arch tag.
+      - name: Assemble production tags
+        if: steps.t.outputs.skip == '0' && steps.t.outputs.prod == 'true'
+        env:
+          AMD64_DIGEST: ${{ steps.amd64.outputs.digest }}
+          ARM64_DIGEST: ${{ steps.arm64.outputs.digest }}
+          ARM64_OUTCOME: ${{ steps.arm64.outcome }}
+          ALLOW_AMD_ONLY: ${{ steps.t.outputs.amd_only }}
+          REPO: repo.anhonesthost.net/cloud-hosting-platform/${{ steps.t.outputs.image_name }}
+          PHPVER: ${{ matrix.phpver }}
+        run: |
+          set -euo pipefail
+          tags=(--tag "php${PHPVER}")
+          [ "$PHPVER" = 85 ] && tags+=(--tag latest)
+          if [ "${ARM64_OUTCOME:-skipped}" != success ] && [ "$ALLOW_AMD_ONLY" != true ]; then
+            for t in "php${PHPVER}" $([ "$PHPVER" = 85 ] && echo latest); do
+              rc=0; info=$(./scripts/index-platforms.sh "$REPO:$t") || rc=$?
+              case "$rc" in
+                0) ;;
+                3) info="not found" ;;
+                *) echo "::error::cannot tell whether $REPO:$t is multi-arch; refusing to overwrite it (fail closed)"; exit 1 ;;
+              esac
+              echo "$REPO:$t currently: $info"
+              case "$info" in
+                *linux/arm64*)
+                  echo "::error::$REPO:$t is multi-arch (has arm64) but arm64 was not built successfully in this run (outcome=${ARM64_OUTCOME:-skipped}). Publishing amd64-only would drop arm64. Re-run with build_arm64=true, or set allow_amd64_only=true to accept that. The immutable tag was still created."
+                  exit 1 ;;
+              esac
+            done
+          fi
+          ./scripts/assemble-multiarch-index.sh \
+            --amd64 "$AMD64_DIGEST" \
+            --arm64 "$ARM64_DIGEST" --arm64-outcome "${ARM64_OUTCOME:-skipped}" \
+            --repo "$REPO" "${tags[@]}"