Fix base64 comment: 0xFB,0xEF,0xBE encodes to "++++", not "+++"

Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: Copilot

tests/ModelContextProtocol.Tests/Protocol/ContentBlockTests.cs

@@ -340,7 +340,7 @@ public static TheoryData<byte[]> Base64TestData()
             new byte[] { 0x00, 0x01 }, // 2 bytes, 1 padding char: "AAE="
             new byte[] { 0x00, 0x01, 0x02 }, // 3 bytes, no padding: "AAEC"
             new byte[] { 0xFF, 0xD8, 0xFF, 0xE0 }, // produces '/' in base64: "/9j/4A=="
-            new byte[] { 0xFB, 0xEF, 0xBE }, // produces '+' in base64: "+++"
+            new byte[] { 0xFB, 0xEF, 0xBE }, // produces '+' in base64: "++++"
         };
 
         // All 256 byte values to exercise the full base64 alphabet

tests/ModelContextProtocol.Tests/Protocol/ResourceContentsTests.cs

@@ -524,7 +524,7 @@ public static TheoryData<byte[]> Base64TestData()
             new byte[] { 0x00, 0x01 }, // 2 bytes, 1 padding char: "AAE="
             new byte[] { 0x00, 0x01, 0x02 }, // 3 bytes, no padding: "AAEC"
             new byte[] { 0xFF, 0xD8, 0xFF, 0xE0 }, // produces '/' in base64: "/9j/4A=="
-            new byte[] { 0xFB, 0xEF, 0xBE }, // produces '+' in base64: "+++"
+            new byte[] { 0xFB, 0xEF, 0xBE }, // produces '+' in base64: "++++"
         };
 
         // All 256 byte values to exercise the full base64 alphabet