ci: fail when generated examples are out of date (#11)

.github/workflows/build.yml

@@ -40,16 +40,21 @@ jobs:
       - name: Set up Rust
         run: rustup show
 
-      # Pinned to match AGENTS.md / Dockerfile.factory: protoc 29.3,
-      # protoc-gen-prost 0.5.0, protoc-gen-tonic 0.5.0 and
-      # protoc-gen-prost-serde 0.4.0. If these drift from the committed
-      # examples/src/gen/ output, this job fails below.
+      # protoc 29.3 must match the version pinned in AGENTS.md, the Makefile
+      # and Dockerfile.factory (the factory image). If this job's toolchain
+      # drifts from those, it will disagree with the committed
+      # examples/src/gen/ output and fail below.
       - name: Set up protoc
         uses: arduino/setup-protoc@v3
         with:
           version: "29.3"
           repo-token: ${{ secrets.GITHUB_TOKEN }}
 
+      # protoc-gen-prost 0.5.0, protoc-gen-tonic 0.5.0 and
+      # protoc-gen-prost-serde 0.4.0 must likewise match AGENTS.md, the
+      # Makefile and Dockerfile.factory. In Go, drift between the pinned
+      # plugin versions and the ones used to produce the committed generated
+      # code was a recurring source of spurious diffs.
       - name: Install prost/tonic/serde protoc plugins
         run: |
           cargo install --locked protoc-gen-prost@0.5.0 protoc-gen-tonic@0.5.0 protoc-gen-prost-serde@0.4.0