chore: update changelog with info about SEP-986 (modelcontextprotocol#1633)

Author: alexhancock

docs/specification/draft/changelog.mdx

@@ -12,6 +12,7 @@ the previous revision, [2025-06-18](/specification/2025-06-18).
 1. Enhance authorization server discovery with support for [OpenID Connect Discovery 1.0](https://openid.net/specs/openid-connect-discovery-1_0.html). (PR [#797](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/797))
 2. Allow servers to expose icons as additional metadata for tools, resources, resource templates, and prompts ([SEP-973](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/973)).
 3. Enhance authorization flows with incremental scope consent via `WWW-Authenticate` ([SEP-835](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/835))
+4. Provide guidance on tool names ([SEP-986](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1603))
 
 ## Minor changes