Run wiki sync on docker runners (skip cleanly without token) (#75)

Co-authored-by: claude <claude@jpaul.io>
Co-committed-by: claude <claude@jpaul.io>

.gitea/workflows/sync-wiki.yml

@@ -1,11 +1,9 @@
 # Render the course (single source of truth = modules/) into the Gitea wiki on
 # every push to main. The wiki is generated BUILD OUTPUT — never hand-edit it.
 #
-# Prerequisites (one-time):
-#   1. An Actions runner is attached to this repo/org (Settings -> Actions -> Runners).
-#   2. A repo secret WIKI_TOKEN holds a token with write access to the wiki
-#      (a PAT/deploy token scoped to repository write is enough — NOT a site-admin token).
-#   3. The wiki is initialized (it is — created with a Home page).
+# Runs on the stack's shared `docker` runners (Linux). To actually push the wiki it
+# needs a repo secret WIKI_TOKEN with wiki write (a scoped PAT/deploy token — NOT a
+# site-admin token). Until that secret exists the job skips cleanly (stays green).
 name: Sync course wiki
 on:
   push:
@@ -20,22 +18,21 @@ on:
 
 jobs:
   sync-wiki:
-    runs-on: ubuntu-latest
+    runs-on: docker
     steps:
-      - uses: actions/checkout@v7
-      - uses: actions/setup-python@v6
-        with:
-          python-version: '3.x'
+      - uses: actions/checkout@v4
       - name: Render and push the wiki
         shell: bash
         env:
           WIKI_TOKEN: ${{ secrets.WIKI_TOKEN }}
         run: |
           set -euo pipefail
+          echo "runner: $(uname -srm) — $(python3 --version 2>/dev/null || echo 'python3 missing')"
           if [ -z "${WIKI_TOKEN:-}" ]; then
-            echo "::error::WIKI_TOKEN secret is not set — see this workflow's header."
-            exit 1
+            echo "::warning::WIKI_TOKEN secret not set — skipping wiki sync. Add the secret to enable auto-sync."
+            exit 0
           fi
+          command -v python3 >/dev/null || { apt-get update && apt-get install -y --no-install-recommends python3; }
           base="git.jpaul.io/justin/ai-workflow-course"
           git clone "https://claude:${WIKI_TOKEN}@${base}.wiki.git" wiki
           python3 tools/build_wiki.py --repo-root . --out wiki \