test: read the bootstrap topology fixture from this repo

Six tests loaded tf-sdk's tests/contract/bootstrap_example.yaml from a
tf-sdk checkout sitting next to this repo. CI clones SRM on its own, so
they failed on every refactor/tf-sdk-wiring pipeline. The file is now
copied, unchanged, to tests/fixtures/tf_sdk_bootstrap_example.yaml (the
same content on tf-sdk's refactor/tfsdk-architecture-alignment) and both
tests read it from there.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>