Generate the course textbook into the wiki from modules/ (CI sync) (#72)

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

tools/README.md

@@ -0,0 +1,41 @@
+# tools/
+
+## `build_wiki.py` — render the course into a wiki
+
+The course wiki (the "textbook" view under the **Wiki** tab) is **generated build
+output**. The single source of truth is `modules/**/README.md` + `capstone/README.md`.
+**Never hand-edit the wiki** — edits there are overwritten on the next sync.
+
+`build_wiki.py` is host-agnostic: it writes Markdown pages into a wiki working
+directory (`Home.md`, `_Sidebar.md`, `_Footer.md`, one page per module + capstone),
+rewriting `lab/…` and repo-root links to absolute URLs back in the main repo (so the
+runnable labs stay in the repo and are linked, never copied into the wiki).
+
+### Run it manually
+
+```bash
+# clone the wiki repo (Gitea)
+git clone https://git.jpaul.io/justin/ai-workflow-course.wiki.git wiki
+
+# render into it
+python3 tools/build_wiki.py --repo-root . --out wiki \
+    --web-base https://git.jpaul.io/justin/ai-workflow-course --branch main --host gitea
+
+# publish
+cd wiki && git add -A && git commit -m "docs(wiki): sync from modules/" && git push
+```
+
+For GitHub, use `--host github` and `--web-base https://github.com/<owner>/<repo>`.
+
+### Automated sync (CI)
+
+- **Gitea:** `.gitea/workflows/sync-wiki.yml` runs on every push to `main` that
+  touches `modules/**`, `capstone/**`, `README.md`, or this generator.
+- **GitHub:** `.github/workflows/sync-wiki.yml` does the same on the mirror.
+
+Both need, one time:
+1. an **Actions runner** attached (Gitea: Settings → Actions → Runners);
+2. a repo secret **`WIKI_TOKEN`** with wiki write (a scoped PAT/deploy token — *not*
+   a site-admin token; on GitHub the default `GITHUB_TOKEN` can't push the wiki);
+3. the wiki **initialized** once (Gitea is already initialized; on GitHub create one
+   page in the UI first so `<repo>.wiki.git` exists).