MCP GraphQL Integration design document - Implemented

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Updates the MCP GraphQL Integration design document to reflect the implemented architecture. Key changes include:

Status Update: Marks the design as implemented (previously ongoing)

Architecture Refinements:

• Renamed McpToolBase → GraphqlTool and moved from lib/gitlab/graphql/mcp/ to app/services/mcp/tools/
• Enhanced Versionable concern with GraphQL-specific methods for operation retrieval and version-specific variable building
• Introduced composite tool pattern for grouping related operations into unified interfaces

Implementation Details:

• Added version metadata support for storing GraphQL operations and operation names
• Documented version-specific build_variables methods (e.g., build_variables_0_2_0)
• Clarified limitation: one mutation operation per tool invocation
• Updated code examples to reflect actual implementation patterns

Documentation Improvements:

• Removed outdated multiple mutations example (replaced with composite tool pattern)
• Added real-world examples: work item notes creation/retrieval tools
• Updated file paths, class names, and method signatures throughout
• Clarified future enhancements: multiple mutations via service-level aggregation

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Commits

• Update MCP GraphQL Integration design document

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