lab: compile from the module's root, so the runtime finds its tools

Both sources sit in tools/, so tsc took tools/ as the root and wrote
dist/index.js, while the runtime loads dist/tools/index.js: the module
started and served nothing.

modules/lab/Dockerfile

@@ -10,7 +10,7 @@ ARG RUNTIME_BASE
 FROM ${BUILD_BASE} AS build
 WORKDIR /app/modules/lab
 COPY . .
-RUN node /app/node_modules/typescript/bin/tsc tools/index.ts tools/runs.ts \
+RUN node /app/node_modules/typescript/bin/tsc tools/index.ts tools/runs.ts --rootDir . \
       --module NodeNext --moduleResolution NodeNext --target ES2022 --outDir dist
 
 FROM ${RUNTIME_BASE}