feat(tools): Add navigation tools

[CalvinAllen]

Description

Implement navigation-related MCP tools to allow AI assistants to navigate code in Visual Studio.

Tools to Implement

• goto_definition - Navigate to symbol definition
• find_references - Find all references to a symbol
• find_symbol - Search for symbols by name

VS APIs

• DTE2.ExecuteCommand("Edit.GoToDefinition")
• DTE2.ExecuteCommand("Edit.FindAllReferences")
• Language services / CodeModel