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.

bench/reachability-benchmark/cases/c/memcpy-overflow/entrypoints.yaml

@@ -0,0 +1,7 @@
+case_id: "c-memcpy-overflow:001"
+entries:
+  cli:
+    - id: "process_buffer"
+      command: "./app"
+      args: ["<length>"]
+      description: "User length forwarded to memcpy without bounds"