feat(real-world-vfc-slice): add labeled OpenSSL/Firefox/Chromium/curl pair corpus

Harvest 176 isolated vuln-vs-fix functions (109 CVEs, 352 training rows)
into benchmarks/pairs/vfc with provenance and a JSONL training manifest.
Score the slice as an honesty dashboard (ousast pairs --slice vfc);
keep the pair gate on the local fixtures only.

benchmarks/pairs/vfc/openssl-cve-2021-3711-pkey_sm2_decrypt/fixed.c

@@ -0,0 +1,28 @@
+/* Provenance: openssl/openssl pkey_sm2_decrypt (fixed).
+ * repo: openssl/openssl
+ * commit: 59f5e75f3bced8fc0e130d72a3f582cf7b480b46
+ * parent: 8c74c9d1ade0fbdab5b815ddb747351b8b839641
+ * commit_url: https://github.com/openssl/openssl/commit/59f5e75f3bced8fc0e130d72a3f582cf7b480b46
+ * cve: CVE-2021-3711
+ * license: OpenSSL License
+ * function: pkey_sm2_decrypt
+ * relpath: crypto/sm2/sm2_pmeth.c
+ */
+
+static int pkey_sm2_decrypt(EVP_PKEY_CTX *ctx,
+                            unsigned char *out, size_t *outlen,
+                            const unsigned char *in, size_t inlen)
+{
+    EC_KEY *ec = ctx->pkey->pkey.ec;
+    SM2_PKEY_CTX *dctx = ctx->data;
+    const EVP_MD *md = (dctx->md == NULL) ? EVP_sm3() : dctx->md;
+
+    if (out == NULL) {
+        if (!sm2_plaintext_size(in, inlen, outlen))
+            return -1;
+        else
+            return 1;
+    }
+
+    return sm2_decrypt(ec, md, in, inlen, out, outlen);
+}