act_runner: add a python312 label (CPython 3.12 + node) for the bot's CI; note that labels are fixed at registration

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -297,7 +297,10 @@ services:
       GITEA_INSTANCE_URL: https://${GIT_HOST:-git.example.com}/
       GITEA_RUNNER_REGISTRATION_TOKEN: ${GITEA_RUNNER_TOKEN:-}   # set by ./registerGiteaRunner.sh
       GITEA_RUNNER_NAME: vanguard-runner
-      GITEA_RUNNER_LABELS: "ubuntu-latest:docker://docker.gitea.com/runner-images:ubuntu-latest,ubuntu-22.04:docker://docker.gitea.com/runner-images:ubuntu-22.04,dotnet:docker://mcr.microsoft.com/dotnet/sdk:10.0,python:docker://python:3.12"
+      # JavaScript actions (checkout, upload-artifact) need node INSIDE the job image, so a label used with
+      # them must point at an image that has it. "python" is bare CPython for plain run: steps; "python312"
+      # adds node and is what the Discord bot's CI uses, so its wheels match the python:3.12-slim runtime.
+      GITEA_RUNNER_LABELS: "ubuntu-latest:docker://docker.gitea.com/runner-images:ubuntu-latest,ubuntu-22.04:docker://docker.gitea.com/runner-images:ubuntu-22.04,dotnet:docker://mcr.microsoft.com/dotnet/sdk:10.0,python:docker://python:3.12,python312:docker://nikolaik/python-nodejs:python3.12-nodejs22"
     volumes:
       - /srv/appdata/act_runner:/data
       - /var/run/docker.sock:/var/run/docker.sock   # jobs run as sibling containers; root-equivalent on the host