fix(oci): Preserve raw manifest bytes for digest calculation and handle string/JSON manifest bodies in OCI registry

ts/oci/classes.ociregistry.ts

@@ -379,7 +379,18 @@ export class OciRegistry extends BaseRegistry {
       };
     }
 
-    const manifestData = Buffer.isBuffer(body) ? body : Buffer.from(JSON.stringify(body));
+    // Preserve raw bytes for accurate digest calculation
+    // Per OCI spec, digest must match the exact bytes sent by client
+    let manifestData: Buffer;
+    if (Buffer.isBuffer(body)) {
+      manifestData = body;
+    } else if (typeof body === 'string') {
+      // String body - convert directly without JSON transformation
+      manifestData = Buffer.from(body, 'utf-8');
+    } else {
+      // Body was already parsed as JSON object - re-serialize as fallback
+      manifestData = Buffer.from(JSON.stringify(body));
+    }
     const contentType = headers?.['content-type'] || headers?.['Content-Type'] || 'application/vnd.oci.image.manifest.v1+json';
 
     // Calculate manifest digest