Per user feedback: the test progression is fundamentally broken. Tests
hotpatch individual state fields (files, rag_enabled, etc.) via set_value
instead of switching to a project that has the right configuration, like
a user would. The session-scoped subprocess's active_project_path leaks
across tests because reset_session() deliberately doesn't reset it.
Documented the 4 red flags:
1. test_rag_phase4_final_verify hotpatches state, never calls _switch_project
2. reset_session() is an incomplete reset masquerading as @clean_baseline
3. sim_base.teardown() is a no-op (cleanup commented out), never switches back
4. index_file silently no-ops on missing files (production bug)
Correct fix: tests should call _switch_project to establish their project
context (like a user), not hotpatch. reset_session() should restore the
original project. sim_base.teardown() should switch back + clean up.
Retracted the 'delete stale files' recommendation — that treats the
symptom, not the defect.