fix(stage1): verify survey design fields

.learnings/ERRORS.md

@@ -2,6 +2,35 @@
 
 Command failures and integration errors.
 
+---
+## [ERR-20260920-042] pdf-runtime-path-mismatch
+
+**Logged**: 2026-09-20
+**Priority**: low
+**Status**: resolved
+**Area**: environment
+
+### Summary
+Neither `pdftotext` nor `pypdf` was available in the project/system Python path used for the first survey-design source extraction attempt.
+
+### Error
+PowerShell could not find `pdftotext`; project Python raised `ModuleNotFoundError: pypdf`.
+
+### Context
+The failures were read-only and occurred before any design decision was recorded.
+
+### Suggested Fix
+Use the Codex workspace PDF runtime returned by the workspace dependency loader for document extraction; keep statistical builders in `.venv-research`.
+
+### Metadata
+- Reproducible: yes
+- Related Files: `research/stage1/survey_design_source_audit.md`
+- Pattern-Key: environment.pdf-runtime-path
+
+### Resolution
+- **Resolved**: 2026-09-20
+- **Notes**: Official guide pages were extracted with the bundled PDF runtime and cross-checked against local fields.
+
 ---
 ## [ERR-20260920-041] gitea-cached-credential-rejected