The runtime keeps the compiler, because it is also the build environment

Every module's recipe starts from this image and invokes the compiler out of
it. Pruning build dependencies made a smaller image that nothing could be
built on.

Dockerfile

@@ -41,10 +41,14 @@ RUN npm --prefix node_modules/@novox/mesh-sdk install --no-audit --no-fund \
 COPY tsconfig.json ./
 COPY src ./src
 RUN npm run build
-# Dropped after compiling rather than reinstalled in the next stage, which would need git there too.
-RUN npm prune --omit=dev
 
-# Everything the modules compile against and run on, and nothing that only the build needed.
+# Everything the modules compile against and run on.
+#
+# **The build dependencies stay, and that is deliberate.** This image is not only what a module runs
+# in — it is also what every module is *compiled* in: a module's recipe starts from this and invokes
+# the compiler out of these same directories. Dropping them would halve the image and break every
+# module that builds on it, which is the sort of tidy-looking change that only fails somewhere else.
+# If the two roles are ever separated, they should be separated deliberately and named separately.
 FROM node:22-bookworm-slim
 WORKDIR /app
 COPY package.json ./