import(stage1): validate YRBS 2021 and 2023 layouts

.learnings/ERRORS.md

@@ -2,6 +2,35 @@
 
 Command failures and integration errors.
 
+---
+## [ERR-20260920-026] sas-input-block-comment-collision
+
+**Logged**: 2026-09-20
+**Priority**: low
+**Status**: resolved
+**Area**: data
+
+### Summary
+The first YRBS fixed-width layout parser matched the words “Input Program” in the SAS header comment instead of the executable `Input` statement.
+
+### Error
+`ValueError: No fields parsed` for the official 2021 SAS input program.
+
+### Context
+The broad first-occurrence regular expression selected a comment fragment. No Parquet or audit output was written.
+
+### Suggested Fix
+Anchor the parser to a line containing only the SAS `Input` keyword, then parse the following field declarations.
+
+### Metadata
+- Reproducible: yes
+- Related Files: `research/stage1/import_yrbs_2021_2023.py`
+- Pattern-Key: parser.comment-keyword-collision
+
+### Resolution
+- **Resolved**: 2026-09-20
+- **Notes**: The input-block expression is line-anchored and the import is rerun from the official files.
+
 ---
 ## [ERR-20260920-036] pdf-text-console-encoding
 
@@ -1055,7 +1084,7 @@ Remove the override and tolerate the harmless warning, or use an actual readable
 - **Notes**: The override is removed; no index changes occurred in the failed attempt.
 
 ---
-## [ERR-20260920-024] parquet-field-name-assumption
+## [ERR-20260920-037] parquet-field-name-assumption
 
 **Logged**: 2026-09-20
 **Priority**: low
@@ -1084,7 +1113,7 @@ Inspect the authoritative schema before column projection and use the source-spe
 - **Notes**: Re-ran the count query against `YEAR` and obtained annual distributions for `YUSUITHK` and `YUSUIPLN`.
 
 ---
-## [ERR-20260920-025] yrbs-attempt-response-shape
+## [ERR-20260920-038] yrbs-attempt-response-shape
 
 **Logged**: 2026-09-20
 **Priority**: medium
@@ -1113,3 +1142,32 @@ Apply the shared five-level frequency mapping to both GSHS and YRBS attempt item
 - **Notes**: Canonical attempt categories are now `zero`, `one`, `two_or_three`, `four_or_five`, and `six_or_more` in both surveys.
 
 ---
+## [ERR-20260920-039] sas-input-parser-edge-cases
+
+**Logged**: 2026-09-20
+**Priority**: low
+**Status**: resolved
+**Area**: data
+
+### Summary
+The first two YRBS fixed-width parser attempts encountered a SAS header-comment keyword collision and the SAS numeric missing token `.`.
+
+### Error
+The first attempt found no layout fields; the second could not convert `.` to a float.
+
+### Context
+Both failures occurred before a complete Parquet/audit output was accepted.
+
+### Suggested Fix
+Anchor the layout parser to a line containing only `Input` and map the SAS numeric missing token `.` to null.
+
+### Metadata
+- Reproducible: yes
+- Related Files: `research/stage1/import_yrbs_2021_2023.py`
+- Pattern-Key: parser.sas-fixed-width-edge-cases
+
+### Resolution
+- **Resolved**: 2026-09-20
+- **Notes**: Both cases are handled explicitly and the official-layout import is rerun from source.
+
+---