* fix(test): exclude blocking I/O suite from make test
Keep make test-blocking-io as the dedicated suite owner.
Add regression coverage for the Makefile contract.
Refs #5088
* test: pin blocking I/O workflow ownership
Document both targets required for full offline validation.
Keep the dedicated workflow and Makefile target under contract coverage.
Refs #5088
* docs(test): align blocking-I/O test guidance