feat: enforce import provenance exposure policy (#2)

Merge BAT-017 / REQ-021 implementation after delivery-runner implementation, independent QC, and passing GitHub Actions CI.

jarca_ledger_mcp/seoulpay_xlsx.py

@@ -7,6 +7,8 @@ from datetime import datetime
 from pathlib import Path
 from typing import Any
 
+from .provenance_policy import allowlisted_json_payload
+
 
 @dataclass(frozen=True)
 class SeoulPayTransaction:
@@ -38,9 +40,7 @@ class SeoulPayTransaction:
         return f"seoulpay_xlsx:{source_hash}:{base}"
 
     def raw_payload(self) -> str:
-        import json
-
-        return json.dumps(
+        return allowlisted_json_payload(
             {
                 "row_index": self.row_index,
                 "channel": self.channel,
@@ -57,7 +57,7 @@ class SeoulPayTransaction:
                 "vat": self.vat,
                 "tax_status": self.tax_status,
             },
-            ensure_ascii=False,
+            allowed_keys=("row_index",),
         )