Harden inquiry participant edge cases

docs/inquiry-participants-proposal.md

@@ -34,6 +34,7 @@ Use explicit role references instead:
   "driver": {
     "nationalCode": "0012345678",
     "birthday": "1370/01/01",
+    "hasDrivingLicense": true,
     "licenseNumber": "123456789",
     "licenseType": "1"
   },
@@ -48,6 +49,8 @@ Use explicit role references instead:
 
 `carBodyPolicyholder` is forbidden for `THIRD_PARTY` and required for `CAR_BODY`. A role is either a new person's identity or a `sameAs` reference, never both. The backend should normalize this input into unique participants plus role assignments.
 
+For the damaged party of a `THIRD_PARTY` case only, the policyholder can be explicitly unresolved with `"thirdPartyPolicyholder": { "unknown": true }`. This is not accepted for the guilty party. Plate-based third-party-policy inquiry is recorded as intentionally skipped because it requires that identity; VIN-based lookup can still run without guessing a person. The driver, owner, personal, ownership, and licence rules remain enforced.
+
 For Driver, `hasDrivingLicense` is required. When it is `true`, both `licenseNumber` and `licenseType` are required; when it is `false`, the licence inquiry is intentionally skipped.
 
 ## Recent ownership transfer and previous plate