fix: registryType mcpbPackageType → mcpb

MCP registry API error: 'unsupported registry type: mcpbPackageType'
Schema examples show valid values: npm, pypi, oci, nuget, mcpb

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server.json

@@ -10,7 +10,7 @@
   "version": "1.31.1",
   "packages": [
     {
-      "registryType": "mcpbPackageType",
+      "registryType": "mcpb",
       "version": "1.31.1",
       "identifier": "https://github.com/masdevid/mt5-quant/releases/download/v1.31.1/mcp-mt5-quant-macos-arm64.tar.gz",
       "fileSha256": "f7e2137c3d223c1af3fe70cb01ce5575874f98a29f732771f4fb816c1d1a5768",