Add receipt input JSON and SHA256 hash for CVSS policy scoring tests

- Introduced a new JSON fixture `receipt-input.json` containing base, environmental, and threat metrics for CVSS scoring.
- Added corresponding SHA256 hash file `receipt-input.sha256` to ensure integrity of the JSON fixture.

tests/Policy/StellaOps.Policy.Scoring.Tests/Fixtures/hashing/receipt-input.json

@@ -0,0 +1,51 @@
+{
+  "baseMetrics": {
+    "ac": "Low",
+    "at": "None",
+    "av": "Network",
+    "pr": "None",
+    "sa": "High",
+    "sc": "High",
+    "si": "High",
+    "ui": "None",
+    "va": "High",
+    "vc": "High",
+    "vi": "High"
+  },
+  "createdAt": "2025-12-03T00:00:00Z",
+  "createdBy": "policy-scorer@stella",
+  "environmentalMetrics": {
+    "ar": "Medium",
+    "cr": "High",
+    "ir": "Medium",
+    "mac": "Low",
+    "mat": "None",
+    "mav": "Network",
+    "mpr": "None",
+    "ms": "Unchanged",
+    "mui": "None",
+    "mva": "High",
+    "mvc": "High",
+    "mvi": "High"
+  },
+  "policyRef": {
+    "hash": "3c1dff9075a14da4c6ae4e8b1e2c9f7569af5f5e90e78c9a0a82f86ccb63d4f9",
+    "id": "cvss-policy-v1",
+    "version": "1.2.0"
+  },
+  "scores": {
+    "base": 9.8,
+    "environmental": 9.4,
+    "threat": 9.8
+  },
+  "supplementalMetrics": {
+    "safety": "Safe"
+  },
+  "tenantId": "tenant-acme",
+  "threatMetrics": {
+    "ad": "High",
+    "rs": "Unreported"
+  },
+  "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/AD:H/RS:X/CR:H/IR:M/AR:M/MAV:N/MAC:L/MAT:N/MPR:N/MUI:N/MVC:H/MVI:H/MVA:H/MS:U",
+  "vulnerabilityId": "CVE-2024-1234"
+}

tests/Policy/StellaOps.Policy.Scoring.Tests/Fixtures/hashing/receipt-input.sha256

@@ -0,0 +1 @@
+bac7e113ad5a27a7fc013608ef3a3b90a3e4d98efbdedbc5953d2c29a3545fef