Why: Mock mode needs a path that drives the real step runner, and the example plugin should fail the host test if its workflow or slot question is wrong.
Evidence: go test ./internal/plugins/ -run TestRepoExamplePluginLoads passed. The brief intent asks 主题是什么? and keeps the topic slot.
Impact: #workflow is only the mock runner. The example plugin itself is in the Dev repo.
Refs: feature/agent-harness-p4
Co-authored-by: Cursor <cursoragent@cursor.com>