ci: record pi-studio version as image label

Adds se.jordbo.pi-devbox.pi-studio-version (e.g. v0.9.36) alongside the
existing SHA label, so 'docker inspect' shows the human-readable version.

Plumbing: resolve-versions exposes studio_tag output -> both studio build
steps pass --build-arg PI_STUDIO_VERSION -> Dockerfile.variant declares
ARG PI_STUDIO_VERSION=none and emits the LABEL. Studio-variant only.

Validated: yq parse OK, resolve run-script bash -n OK. No tag.

.gitea/workflows/docker-publish.yml

@@ -135,6 +135,7 @@ jobs:
       toolkit_ref: ${{ steps.resolve.outputs.toolkit_ref }}
       extensions_ref: ${{ steps.resolve.outputs.extensions_ref }}
       studio_ref: ${{ steps.resolve.outputs.studio_ref }}
+      studio_tag: ${{ steps.resolve.outputs.studio_tag }}
       mempalace_toolkit_ref: ${{ steps.resolve.outputs.mempalace_toolkit_ref }}
     steps:
       - name: Resolve pi version + companion refs
@@ -227,6 +228,7 @@ jobs:
           fi
           require_sha PI_STUDIO_REF "$STUDIO_REF"
           echo "studio_ref=${STUDIO_REF}" >> "$GITHUB_OUTPUT"
+          echo "studio_tag=${STUDIO_TAG}" >> "$GITHUB_OUTPUT"
 
           echo "Resolved PI_VERSION=${PI_VERSION}"
           echo "Resolved PI_FORK_REF=${FORK_REF}, PI_OBSMEM_REF=${OBSMEM_REF}"
@@ -413,6 +415,7 @@ jobs:
             PI_EXTENSIONS_REF=${{ needs.resolve-versions.outputs.extensions_ref }}
             INSTALL_STUDIO=true
             PI_STUDIO_REF=${{ needs.resolve-versions.outputs.studio_ref }}
+            PI_STUDIO_VERSION=${{ needs.resolve-versions.outputs.studio_tag }}
             MEMPALACE_TOOLKIT_REF=${{ needs.resolve-versions.outputs.mempalace_toolkit_ref }}
             RELEASE_TAG=smoke-studio
             SOURCE_REVISION=${{ github.sha }}
@@ -554,6 +557,7 @@ jobs:
           TOOLKIT_REF: ${{ needs.resolve-versions.outputs.toolkit_ref }}
           EXTENSIONS_REF: ${{ needs.resolve-versions.outputs.extensions_ref }}
           STUDIO_REF: ${{ needs.resolve-versions.outputs.studio_ref }}
+          STUDIO_TAG: ${{ needs.resolve-versions.outputs.studio_tag }}
           MEMPALACE_TOOLKIT_REF: ${{ needs.resolve-versions.outputs.mempalace_toolkit_ref }}
         run: |
           set -euo pipefail
@@ -576,6 +580,7 @@ jobs:
                 --build-arg "MEMPALACE_TOOLKIT_REF=${MEMPALACE_TOOLKIT_REF}" \
                 --build-arg "INSTALL_STUDIO=true" \
                 --build-arg "PI_STUDIO_REF=${STUDIO_REF}" \
+                --build-arg "PI_STUDIO_VERSION=${STUDIO_TAG}" \
                 --build-arg "RELEASE_TAG=${RELEASE_TAG}" \
                 --build-arg "BUILD_DATE=${BUILD_DATE}" \
                 --build-arg "SOURCE_REVISION=${GITHUB_SHA:-}" \