Update changelog with additional SEPs and governance updates (modelcontextprotocol#1807)

Add breaking changes for tasks primitive (SEP-1686) and tool calling in sampling (SEP-1577). Include minor changes for OAuth improvements (SEP-985, SEP-991), elicitation enhancements (SEP-1034, SEP-1036), and JSON Schema default (SEP-1613). Add governance section covering protocol governance (SEP-932), communication practices (SEP-994), working groups (SEP-1302), version management (SEP-1309), and SDK tiering (SEP-1730).

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Co-authored-by: Claude <[email protected]>

Author: dsp-ant

docs/specification/draft/changelog.mdx

@@ -26,11 +26,21 @@ the previous revision, [2025-06-18](/specification/2025-06-18).
 3. Updated the [Security Best Practices guidance](https://modelcontextprotocol.io/specification/draft/basic/security_best_practices).
 4. Clarify that input validation errors should be returned as Tool Execution Errors rather than Protocol Errors to enable model self-correction ([SEP-1303](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1303)).
 5. Support polling SSE streams by allowing servers to disconnect at will ([SEP-1699](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1699)).
+6. Align OAuth 2.0 Protected Resource Metadata discovery with RFC 9728, making `WWW-Authenticate` header optional with fallback to `.well-known` endpoint ([SEP-985](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/985)).
+7. Add support for default values in all primitive types (string, number, enum) for elicitation schemas ([SEP-1034](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1034)).
+8. Establish JSON Schema 2020-12 as the default dialect for MCP schema definitions ([SEP-1613](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1613)).
 
 ## Other schema changes
 
 1. Decouple request payloads from RPC method definitions into standalone parameter schemas. ([SEP-1319](https://github.com/modelcontextprotocol/specification/issues/1319), PR [#1284](https://github.com/modelcontextprotocol/specification/pull/1284))
 
+## Governance and process updates
+
+1. Formalize Model Context Protocol governance structure ([SEP-932](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/932)).
+2. Establish shared communication practices and guidelines for the MCP community ([SEP-994](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/994)).
+3. Formalize Working Groups and Interest Groups in MCP governance ([SEP-1302](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1302)).
+4. Establish SDK tiering system with clear requirements for feature support and maintenance commitments ([SEP-1730](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1730)).
+
 ## Full changelog
 
 For a complete list of all changes that have been made since the last protocol revision,