Replaces placeholder with full csharp@0.1.0 plugin. Adds helper/
package (locate, process, client, protocol) for JSON-RPC over stdio
to ctx-roslyn-helper. project.go finds .sln (fallback: single .csproj),
loads it, retrieves projectSummary, formats dense markdown with project
details, reference graph, and multi-targeting section.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
