Keep the dev tag check strict and default the tag in the workflow

The earlier script default broke the tests that reject empty tags.
The workflow now falls back to dev-<full commit SHA> for manual runs.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitea/workflows/publish-image.yml

@@ -35,7 +35,7 @@ jobs:
         env:
           EVENT_NAME: ${{ github.event_name }}
           GIT_REF: ${{ github.ref }}
-          INPUT_TAG: ${{ github.event.inputs.tag || inputs.tag }}
+          INPUT_TAG: ${{ github.event.inputs.tag || inputs.tag || format('dev-{0}', github.sha) }}
           SERVER_URL: ${{ github.server_url }}
           REPOSITORY: ${{ github.repository }}
         run: node scripts/image-publication.mjs