feat(tools): add dependency graph visualization tools

[CalvinAllen]

Description

Add dependency graph visualization tools that produce visual graph output for type, namespace, and project dependencies. Builds on the analysis data from #82 (which provides type_dependency_graph, project_dependency_graph, circular_dependency_detection) by adding visualization-specific output formats.

Tools to Implement

Tool	Description
graph_type_dependencies	Generate a visual dependency graph for types in a file/project/namespace
graph_project_dependencies	Generate a visual project-to-project dependency graph for the solution
graph_namespace_dependencies	Generate a visual namespace dependency graph
graph_inheritance	Generate an inheritance/implementation hierarchy graph for a type
graph_call_graph	Generate a visual call graph for a method (callers/callees)
graph_circular_dependencies	Highlight circular dependency cycles in a visual graph

Output Formats

• Mermaid — text-based, renderable in markdown (GitHub, VS preview)
• DOT (Graphviz) — widely supported, can generate SVG/PNG
• JSON — structured data for custom rendering

Each tool should accept an outputFormat parameter defaulting to Mermaid.

Notes

• Depends on feat(tools): add Roslyn-based deep C# analysis tools #82 for underlying Roslyn analysis data
• Visualization is the differentiator — raw data already planned in feat(tools): add Roslyn-based deep C# analysis tools #82
• Mermaid as default makes output immediately useful in chat/markdown contexts
• Competitor reference: RoslynMcp graph_* tools (10 tools)