Add changelog entry for SEP-1330 elicitation enum schema types

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: chr-hertel

CHANGELOG.md

@@ -8,6 +8,7 @@ All notable changes to `mcp/sdk` will be documented in this file.
 * Add built-in authentication middleware for HTTP transport using OAuth
 * Add client component for building MCP clients
 * Add `Builder::setReferenceHandler()` to allow custom `ReferenceHandlerInterface` implementations (e.g. authorization decorators)
+* Add elicitation enum schema types per SEP-1330: `TitledEnumSchemaDefinition`, `MultiSelectEnumSchemaDefinition`, `TitledMultiSelectEnumSchemaDefinition`
 
 0.4.0
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