build(stage1): create primary outcome response layer

.learnings/ERRORS.md

@@ -2,6 +2,35 @@
 
 Command failures and integration errors.
 
+---
+## [ERR-20260920-040] system-python-missing-project-package
+
+**Logged**: 2026-09-20
+**Priority**: low
+**Status**: resolved
+**Area**: environment
+
+### Summary
+The first response-long build was launched with system Python, which does not contain the locked project package set.
+
+### Error
+`ModuleNotFoundError: No module named 'duckdb'`
+
+### Context
+The import failed before source data were read or an output table was created. The project environment is `.venv-research`.
+
+### Suggested Fix
+Run research builders with `.venv-research/Scripts/python.exe` and reserve system Python for dependency-free diagnostics.
+
+### Metadata
+- Reproducible: yes
+- Related Files: `research/stage1/build_responses_long.py`, `research/audit/environment_audit.md`
+- Pattern-Key: environment.wrong-python-runtime
+
+### Resolution
+- **Resolved**: 2026-09-20
+- **Notes**: Re-ran with the locked project Python; the long table and independent checks completed.
+
 ---
 ## [ERR-20260920-026] sas-input-block-comment-collision