fix: restore gnomAD and expression evidence layers for complete 6-layer scoring

Three bugs prevented gnomAD and expression data from contributing to scores:
1. gnomAD COLUMN_VARIANTS mapped "gene" (HGNC symbol) to gene_id instead of
   gene_symbol, causing JOIN miss with gene_universe (Ensembl IDs)
2. Expression HPA data was fetched but never merged (lf_hpa unused)
3. GTEx versioned Ensembl IDs (ENSG*.5) didn't match gene_universe

Results: gnomAD 78.5% coverage, expression 87.4%, 19946 genes with ≥4 layers.
HIGH tier refined from 44 → 18 candidates. Validation PASSED (CDH23 96.5th pctl).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

data/report/candidates.provenance.yaml

@@ -1,12 +1,12 @@
-generated_at: '2026-02-15T20:47:53.707513+00:00'
+generated_at: '2026-02-15T21:13:11.954116+00:00'
 output_files:
 - candidates.tsv
 - candidates.parquet
 statistics:
-  total_candidates: 19342
-  high_count: 44
-  medium_count: 7268
-  low_count: 12030
+  total_candidates: 21103
+  high_count: 18
+  medium_count: 9577
+  low_count: 11508
 column_count: 22
 column_names:
 - gene_id

data/report/reproducibility.json

@@ -1,6 +1,6 @@
 {
-  "run_id": "0bcdae80-84c2-486b-809a-36040ce4821d",
-  "timestamp": "2026-02-15T20:47:54.482074+00:00",
+  "run_id": "e7486ff1-f9be-403b-a68d-115fc845f4a1",
+  "timestamp": "2026-02-15T21:13:12.288563+00:00",
   "pipeline_version": "0.1.0",
   "parameters": {
     "gnomad": 0.2,
@@ -49,9 +49,9 @@
   ],
   "validation_metrics": {},
   "tier_statistics": {
-    "total": 19342,
-    "high": 44,
-    "medium": 7268,
-    "low": 12030
+    "total": 21103,
+    "high": 18,
+    "medium": 9577,
+    "low": 11508
   }
 }

data/report/reproducibility.md

@@ -1,7 +1,7 @@
 # Pipeline Reproducibility Report
 
-**Run ID:** `0bcdae80-84c2-486b-809a-36040ce4821d`
-**Timestamp:** 2026-02-15T20:47:54.482074+00:00
+**Run ID:** `e7486ff1-f9be-403b-a68d-115fc845f4a1`
+**Timestamp:** 2026-02-15T21:13:12.288563+00:00
 **Pipeline Version:** 0.1.0
 
 ## Parameters
@@ -39,7 +39,7 @@
 
 ## Tier Statistics
 
-- **Total Candidates:** 19342
-- **HIGH:** 44
-- **MEDIUM:** 7268
-- **LOW:** 12030
+- **Total Candidates:** 21103
+- **HIGH:** 18
+- **MEDIUM:** 9577
+- **LOW:** 11508