ci(docs): build the MkDocs site with --strict in CI (refs #173) (#189)

refs #173. This is the minimum step from the issue: the site is now **built** in CI, not **published**. Publishing still needs an ADR (Gitea has no built-in Pages) or a CLAUDE.md §12 correction, so the issue stays open.

- `make docs`: creates a throwaway `.venv-docs`, installs pinned `mkdocs==1.6.1` and `mkdocs-material==9.7.7`, then runs `mkdocs build --strict`. The target is also added to `make ci`.
- New `docs` job in `ci.yaml` (`setup-python@v5`, then `make docs`).
- Red, then green: the first commit fails on a link from `runbooks/ci.md` to a file outside `docs/`; the second turns that link into plain code.

**Dependency (§13):** mkdocs and mkdocs-material were already the site's declared toolchain (`mkdocs.yml`) but were never installed anywhere. They give a strict link/nav/theme check. Replacing them means writing our own Markdown link checker, and `check-docs-nav.py` already covers only the nav half. Risk: Material warns that MkDocs 2.0 drops its plugin/theme system, so both are pinned exactly. No ADR, since this adds no new decision beyond what `mkdocs.yml` already assumes.

Verified locally: `make docs` → `Documentation built in 0.87 seconds`.

🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #189

.gitea/workflows/ci.yaml

@@ -98,6 +98,17 @@ jobs:
           [ -n "${GITHUB_STEP_SUMMARY:-}" ] || exit 0
           python3 infra/trx-summary.py TestResults >> "$GITHUB_STEP_SUMMARY"
 
+  # The docs site must build with --strict (#173). setup-python so `make docs` can
+  # create its venv regardless of what the runner image ships.
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: https://github.com/actions/checkout@v4
+      - uses: https://github.com/actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - run: make docs
+
   # Frontend (Nx/Angular) lane: install with pnpm, then Nx lint + test + build.
   frontend:
     runs-on: ubuntu-latest

.gitignore

@@ -61,3 +61,7 @@ __pycache__/
 TestResults/
 test-output/
 tests/e2e/playwright-report.json
+
+# MkDocs build (`make docs`)
+.venv-docs/
+site/

Makefile

@@ -43,11 +43,11 @@ export DOCKER_HOST := unix://$(PODMAN_SOCK)
 endif
 endif
 
-.PHONY: ci lint build unit mutation frontend integration verify verify-up verify-acl verify-nrc verify-projection verify-bff verify-domain verify-observability verify-tracing verify-metrics verify-objecttypen verify-objecten verify-registerrecord verify-objecten-notifications verify-notifications smoke up down local verify-local local-down changelog openzaak-up openzaak-smoke openzaak-seed openzaak-down stack-up stack-smoke stack-down keycloak-up keycloak-smoke keycloak-down flowable-up flowable-smoke flowable-down k8s-lint k8s-drift k8s-registry k8s-images k8s-seed k8s-up k8s-reseed k8s-portals k8s-down k8s-purge help
+.PHONY: ci lint build unit mutation frontend docs integration verify verify-up verify-acl verify-nrc verify-projection verify-bff verify-domain verify-observability verify-tracing verify-metrics verify-objecttypen verify-objecten verify-registerrecord verify-objecten-notifications verify-notifications smoke up down local verify-local local-down changelog openzaak-up openzaak-smoke openzaak-seed openzaak-down stack-up stack-smoke stack-down keycloak-up keycloak-smoke keycloak-down flowable-up flowable-smoke flowable-down k8s-lint k8s-drift k8s-registry k8s-images k8s-seed k8s-up k8s-reseed k8s-portals k8s-down k8s-purge help
 
 ## ci: run the full pipeline — lint, build, unit, mutation, frontend, verify (mirrors Gitea Actions)
 ## `verify` is the live-stack stage (full stack up once → ACL + notification checks).
-ci: lint build unit mutation frontend verify
+ci: lint build unit mutation frontend docs verify
 
 ## frontend: install deps and run the Nx lint/test/build for the portals (pnpm + Node required)
 # Tests run in their own phase, ahead of the build. The @angular/build:unit-test
@@ -81,6 +81,15 @@ unit:
 	python3 infra/test_playwright_summary.py
 	python3 infra/test_portal_caddyfiles.py
 
+## docs: build the MkDocs site with --strict (a broken link or nav entry fails)
+# Pinned in a throwaway venv: Material 9.7 is the last line on MkDocs 1.x, and MkDocs
+# 2.0 drops the plugin/theme system this site relies on. Publishing is a separate
+# decision (#173); this only proves the site builds.
+docs:
+	python3 -m venv .venv-docs
+	.venv-docs/bin/pip install --quiet mkdocs==1.6.1 mkdocs-material==9.7.7
+	.venv-docs/bin/mkdocs build --strict
+
 ## mutation: run the Stryker.NET ratchet on each service with branching logic (fails below baseline)
 # Stryker is pinned as a local dotnet tool (.config/dotnet-tools.json); `tool restore`
 # makes `make mutation` work from a fresh clone. Each service owns its config + break

docs/runbooks/ci.md

@@ -19,6 +19,7 @@ and CI cannot drift:
 | `build` | `make build` → `dotnet build … -c Release` | .NET 10 SDK |
 | `unit` | `make unit` → `dotnet test … -c Release --filter "Category!=Integration"` | .NET 10 SDK |
 | `frontend` | `make frontend` → Nx lint/test/build for the four portals | pnpm + Node |
+| `docs` | `make docs` → `mkdocs build --strict` in a pinned venv (fails on a broken link or nav entry; the site is not published yet, #173) | Python 3 |
 | `k8s` | `make k8s-lint` (render + schema-check the Helm chart) → `make k8s-drift` (chart still describes the same stack as `infra/docker-compose.yml`) | pinned `helm` binary + `docker compose` |
 | `mutation` | `make mutation` → `dotnet tool restore` → `dotnet stryker` (ACL); uploads the HTML report as an artifact | .NET 10 SDK |
 | `verify-stack` | **push to `main` only, skipped on PRs** (#182) — the single live-stack stage — steps: `make verify-up` (full stack up + health, the DoD smoke) → `make verify-acl` (ACL ↔ OpenZaak) → `make verify-nrc` (OpenZaak → NRC delivery) → `make down` | container engine + egress (base images, nuget, `selectielijst.openzaak.nl`) |
@@ -57,7 +58,7 @@ dotnet tool (`.config/dotnet-tools.json`), so it runs identically locally and in
 make mutation     # dotnet tool restore + dotnet stryker on the ACL
 ```
 
-Config lives in [`services/acl/stryker-config.json`](../../services/acl/stryker-config.json).
+Config lives in `services/acl/stryker-config.json`.
 It runs in **solution mode** against `Acl.slnx`, mutating the two projects under test
 (`Acl.Application`, `Acl.Infrastructure`); `Acl.Api` has no tests and is skipped.
 `Acl.slnx` leaves out `Acl.IntegrationTests`: it needs a live OpenZaak, and Stryker