* test(e2e): add enum values, auto-discovering label gates and secret hiding for e2e metadata
* test(e2e): tag router, batches and mcp tests with Subject metadata and record client steps
* test(e2e): leave the batches cleanup harness unit tests untagged
* docs(e2e): name every markerless harness test file that carries no Subject
* test(e2e): keep the step discovery comprehensions to one for clause
* test(e2e): name every driven model on the vllm batch, prompt caching and complexity router subjects