Run journey CI in a pinned Python environment

Assistant: codex
Assistant-Model: gpt-6-astra
Assistant-Session: 01a092fe-13b1-7f12-ac74-7d258af4d79c

.forgejo/workflows/journeys.yaml

@@ -6,15 +6,18 @@ on:
   workflow_dispatch:
 jobs:
   journeys:
-    runs-on: self-hosted
+    runs-on: ubuntu-latest
+    container:
+      image: python:3.12-slim@sha256:d764629ce0ddd8c71fd371e9901efb324a95789d2315a47db7e4d27e78f1b0e9
     steps:
       - name: Test the exact commit
         run: |
           set -eu
           mkdir -p journey-source
-          curl -fsSL "https://forgejo.coulomb.social/${GITHUB_REPOSITORY}/archive/${GITHUB_SHA}.tar.gz" -o journey-source.tar.gz
+          python -c 'import os, urllib.request; urllib.request.urlretrieve("https://forgejo.coulomb.social/" + os.environ["GITHUB_REPOSITORY"] + "/archive/" + os.environ["GITHUB_SHA"] + ".tar.gz", "journey-source.tar.gz")'
           tar xzf journey-source.tar.gz -C journey-source --strip-components=1
           cd journey-source
-          PYTHONDONTWRITEBYTECODE=1 make test
-          PYTHONDONTWRITEBYTECODE=1 make test-journeys JOURNEY_ARGS="--report journey-report.json"
+          PYTHONDONTWRITEBYTECODE=1 PYTHONPATH=src python -m unittest discover -s tests
+          PYTHONDONTWRITEBYTECODE=1 PYTHONPATH=src python scripts/check_layer_conformance.py --report
+          PYTHONDONTWRITEBYTECODE=1 python scripts/run_journey_suites.py --report journey-report.json
           cat journey-report.json