For AI agents: the complete documentation index is available at https://scriptedalchemy.github.io/agent-bundle/llms.txt, the full documentation bundle is available at https://scriptedalchemy.github.io/agent-bundle/llms-full.txt, and this page is available as Markdown at https://scriptedalchemy.github.io/agent-bundle/api/interfaces/test.ContractMatrixProgressSource.md.
The explicit progress path a non-SDK client exposes to lifecycle fixtures.
Returns the unsubscribe; an SDK Client needs none because its handler map
is observed directly.
