fix: adjust mcp schema validation and add default path support

Updated `mcp.json` to enhance validation by supporting `anyOf` schema for `entity` properties and refined `role` typing. Introduced default `path` property for MCP system API and aligned build assets configuration accordingly.

app/internal/docs.build-assets.ts

@@ -7,6 +7,7 @@ async function generate() {
          server: {
             mcp: {
                enabled: true,
+               path: "/mcp",
             },
          },
          auth: {