Integrate SPARC into ContextForge MCP Gateway

[vinodmut]

We have an example plugin for the JSON processor: https://github.com/IBM/mcp-context-forge/tree/main/plugins/altk_json_processor

We can have a similar one SPARC. There is a a dependency on this PR getting merged into the gateway first: IBM/mcp-context-forge#1208
That is needed so SPARC can return natural language explanations for why a tool call is not possible, in order for the calling agent to retry the tool call with different arguments.