ci: provoke pipeline (touch Dockerfile + code)

Trivial comment changes to exercise the new CI orchestration: the
docker job should rebuild+push the builder image first, then test
and docs run against the fresh image.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Dockerfile.builder

@@ -1,4 +1,4 @@
-# KPN++ Builder Image
+# KPN++ Builder Image  (CI: pipeline trigger)
 # Pre-built image with GCC, CMake, Ninja, and Python dev headers for building and testing KPN++
 # Build: docker build -f Dockerfile.builder -t gitea.tourolle.paris/dtourolle/kpnpp-builder:latest .
 # Push:  docker push gitea.tourolle.paris/dtourolle/kpnpp-builder:latest