fix(ci): initialise the published repo when its directory is empty

The publish step created the OSTree repo only when the directory was
missing. On the runner host the web root exists before the first
publish, as an empty directory, so the init was skipped and
build-commit-from failed with `opendir(objects)`. The check now looks
for the repo's config file.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.forgejo/workflows/ci.yaml

@@ -134,7 +134,9 @@ jobs:
           FLATPAK_GPG_KEY_ID=$(cat /run/crafter-flatpak/key-id)
           # The live repo is the canonical copy; builds are promoted into it,
           # never built into it.
-          [ -d "$REPO_DIR" ] || ostree init --repo="$REPO_DIR" --mode=archive
+          # Keyed on the repo's config file, not the directory: the web root
+          # may exist as an empty directory before the first publish.
+          [ -f "$REPO_DIR/config" ] || ostree init --repo="$REPO_DIR" --mode=archive
           flatpak build-commit-from --src-repo=repo \
             --gpg-sign="$FLATPAK_GPG_KEY_ID" --gpg-homedir="$GNUPGHOME" \
             "$REPO_DIR" "app/$APP_ID/x86_64/${{ steps.meta.outputs.branch }}"