Agent-pipeline e2e is the only coverage of the skill chain and CI never runs it #397

PR #393 fixed tests/e2e/test_add_flush_agent_pipeline_e2e.py so it actually exercises the agent-skill chain — before that fix it structurally could not, and that is why a defect making the chain fail 4/4 reached a release.

The original failure had two layers:

1. tests/conftest.py:68-88 is an autouse fixture forcing EmbeddingCapability(provider=None) for every test (hermeticity — correct in itself). trigger_skill_clustering and extract_agent_skill both body-guard on get_embedding_capability().available, so both returned early. Measured log counts from an actual run: agent_case_extracted=5, skill_cluster_updated=0, agent_skills_extracted=0, strategy_gated_off_embedding_unavailable=10.
2. Its three skill assertions were assert len(...) >= 0 — always true. The inline comment rationalized this as LLM-dependent flakiness; the count was in fact necessarily zero.

#393 opts the test in to a real embedding capability and gives it a meaningful floor plus a dead-letter assertion. But it keeps the slow + live_llm markers, and CI injects no provider credentials — so this remains the only end-to-end coverage of the chain, and it still never runs automatically.

Worth deciding how to close that gap. Options: a scheduled (nightly / weekly) job with credentials in secrets, running just the live_llm set; a recorded-fixture replay so the chain can be exercised without credentials (the examples/langfuse trace-replay work may be reusable); or accept it and add a release-checklist step that runs it manually.

Related: the same class of gap likely applies to other live_llm tests — worth auditing which of them, if any, are the sole coverage of their path.