chore: update workflow stub to use prebuilt runner image

Switch from python:3.12-slim + apt/pip installs to
novoyuuparosk-wiki-runner:latest. Removes the two install steps.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/publish-songs.yml

@@ -19,14 +19,9 @@ jobs:
   publish:
     runs-on: ubuntu-latest
     container:
-      image: python:3.12-slim
+      image: novoyuuparosk-wiki-runner:latest
 
     steps:
-      - name: Install system deps
-        run: |
-          apt-get update -qq
-          apt-get install -y --no-install-recommends git pandoc ca-certificates
-
       - name: Checkout ncmr-songs
         env:
           FAPAT: ${{ secrets.FAPAT }}
@@ -41,9 +36,6 @@ jobs:
           URL_TO_GITEA: ${{ vars.URL_TO_GITEA }}
         run: git clone "http://mikkeli:${FAPAT}@${URL_TO_GITEA#http://}/mikkeli/novoyuuparosk-auto-wiki" auto-wiki
 
-      - name: Install Python deps
-        run: pip install --no-cache-dir -r auto-wiki/pipelines/songs/requirements.txt
-
       - name: Detect changed files
         id: diff
         run: |