Gitea workflow: sparse checkout, diagnostic step removed

Checkout is a cone-mode sparse checkout of server and infra/backup (the
two build contexts), which makes actions/checkout fetch with
--filter=blob:none. fetch-depth stays 0: with depth 1, fetch-tags only
auto-follows tags on the fetched commit, and the version step needs
every v1.0.* tag. The temporary secrets diagnostic step is gone and the
header names kvitt_cicd as the owner's user-level secret.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQd3pEP9UeN2uifbHknQ7B

.gitea/workflows/build-images.yaml

@@ -6,8 +6,8 @@
 # plain HTTP), each tagged with the version vMAJOR.MINOR.PATCH and `latest`, then pushes the git tag of that version.
 # On the Kvitt Pi: /opt/kvitt/deploy.sh <version>.
 #
-# Secret: `kvitt_cicd`, a repository secret holding a Gitea access token with scope write:package of the user that
-# pushes (owner step, infra/README.md). It is used only for `docker login`; the git tag push at the end goes through
+# Secret: `kvitt_cicd`, a user-level secret of the repository owner (Gitea gives a repository its owner's secrets)
+# holding a Gitea access token with scope write:package of the user that pushes (owner step, infra/README.md). It is used only for `docker login`; the git tag push at the end goes through
 # the credentials actions/checkout stored (the job's own token), not this secret, so it needs no write:repository.
 #
 # RISK: the runner is a Raspberry Pi 3 with 1 GB RAM and the server image compiles about 232 Rust crates
@@ -44,25 +44,6 @@ jobs:
     steps:
       - name: Install Git and Docker CLI
         run: apk add --no-cache git docker-cli docker-cli-buildx
-      # TEMPORARY (D-120 follow-up): remove this step once the cause of the empty `kvitt_cicd` secret is known.
-      # Prints only lengths (0 = absent or empty) and non-secret context values, never a secret value.
-      # Gitea stores secret names upper-cased and the expression lookup is case-insensitive; the upper-case line
-      # tests that on this runner. babymonitor_cicd is the owner's known-working user-level secret (control).
-      # GITEA_TOKEN and github.token are the job's automatic token.
-      - name: Diagnose secrets (temporary, D-120 follow-up)
-        run: |
-          A='${{ secrets.kvitt_cicd }}'; printf 'secrets.kvitt_cicd length: %s\n' "${#A}"
-          A='${{ secrets.KVITT_CICD }}'; printf 'secrets.KVITT_CICD length: %s\n' "${#A}"
-          A='${{ secrets.babymonitor_cicd }}'; printf 'secrets.babymonitor_cicd length: %s\n' "${#A}"
-          A='${{ secrets.GITEA_TOKEN }}'; printf 'secrets.GITEA_TOKEN length: %s\n' "${#A}"
-          A='${{ github.token }}'; printf 'github.token length: %s\n' "${#A}"
-          unset A
-          printf 'github.repository: %s\n' '${{ github.repository }}'
-          printf 'github.repository_owner: %s\n' '${{ github.repository_owner }}'
-          printf 'github.actor: %s\n' '${{ github.actor }}'
-          printf 'github.event_name: %s\n' '${{ github.event_name }}'
-          printf 'github.ref: %s\n' '${{ github.ref }}'
-          printf 'github.server_url: %s\n' '${{ github.server_url }}'
       - name: Log in to Gitea Container Registry
         # The owner's proven form: the secret interpolated into the run line (act_runner masks it in the log).
         # The env-based form (env: REGISTRY_TOKEN: ${{ secrets.kvitt_cicd }}) came through empty on act_runner 0.6.1.
@@ -84,6 +65,18 @@ jobs:
         with:
           # Tells the action to use the local 'git' binary installed above
           set-safe-directory: 'true'
+          # Only the two build contexts: server/Dockerfile copies its own context (server/, Cargo workspace,
+          # migrations and the import's category table included) and infra/backup/Dockerfile copies backup.sh and
+          # healthcheck.sh. Cone mode also checks out the files at the root and directly in infra/. A sparse
+          # checkout makes the action fetch with --filter=blob:none, so only the blobs of these paths are downloaded
+          # (not the Android screenshot goldens).
+          sparse-checkout: |
+            server
+            infra/backup
+          sparse-checkout-cone-mode: true
+          # Full commit and tag history (trees and commits only, no blobs, because of the filter above): "Determine
+          # Version" needs every v1.0.* tag. With fetch-depth 1, fetch-tags: true only drops --no-tags, so git
+          # fetches just the tags that point at the fetched commit, not the older v1.0.N.
           fetch-depth: 0
       - name: Determine Version
         run: |
@@ -132,6 +125,7 @@ jobs:
             rm -f "/tmp/kvitt-$name.metadata.json"
           done
       - name: Tag and Push Version
+        # The tag points at HEAD, which the remote already has; works with the sparse, blob-filtered checkout.
         run: |
           git tag "$VERSION"
           git push origin "$VERSION"