Currently all playground examples are built with NGC, and most of the HTML resources are automatically inlined. Surprisingly NGC is able to resolve the relative component assets even though these aren't specified in the `assets`. This seems to work because NGC resolves the files in the execroot where the files are present (if Bazel doesn't use sandboxing). Issue is tracked with TOOL-667 PR Close #28562
How to serve the examples
All playground examples are built and served with Bazel. Below is an example that demonstrates how a specific example can be built and served with Bazel:
# e.g. src/zippy_component
yarn bazel run modules/playground/src/zippy_component:devserver
# e.g. src/upgrade
yarn bazel run modules/playground/src/upgrade:devserver