Consolidate Cursor-specific rules into AGENTS.md and remove tool-specific files

- Add release process section to AGENTS.md with changelog guidelines
- Include Keep a Changelog format requirements and entry formatting rules
- Remove .cursor/rules/release-changelogs.mdc to favor universal AGENTS.md format
- Ensure all AI coding assistants have access to release documentation guidelines

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: atesgoral

.cursor/rules/release-changelogs.mdc

@@ -33,6 +33,16 @@ This is the official Ruby SDK for the Model Context Protocol (MCP), implementing
 - Include clear, descriptive commit messages
 - Releases are triggered by updating version in `lib/mcp/version.rb` and merging to main
 
+## Release process
+- Follow [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) format in CHANGELOG.md
+- Update CHANGELOG.md before cutting releases
+- Use git history and PR merge commits to construct changelog entries
+- Format entries as: "Terse description of the change (#nnn)"
+- Keep entries in flat list format (no nesting)
+- Git tags mark commits that cut new releases
+- Exclude maintenance PRs that don't concern end users
+- Check upstream remote for PRs if available
+
 ## Architecture overview
 
 ### Core Components