feat(tools): add window management tools

[CalvinAllen]

Summary

• Add window_list, window_activate, toolwindow_show, and toolwindow_hide MCP tools for interacting with Visual Studio windows
• toolwindow_show uses friendly names (e.g., SolutionExplorer, ErrorList, Output) mapped to DTE View.* commands instead of requiring GUIDs
• Returns the list of supported tool window names when an invalid name is provided

New Tools

Tool	Description
window_list	List all open windows with caption, kind, visibility, and GUID
window_activate	Activate/focus a window by caption
toolwindow_show	Show a tool window by well-known name
toolwindow_hide	Hide/close a tool window by caption

Supported Tool Windows

SolutionExplorer, ErrorList, Output, TeamExplorer, Terminal, TaskList, Properties, Toolbox, FindResults, Bookmarks

Test plan

• Build solution with dotnet build src/CodingWithCalvin.MCPServer.slnx — verified passing
• Verify window_list returns all open windows with correct kind classification
• Verify window_activate focuses the correct window by caption
• Verify toolwindow_show opens known tool windows (e.g., SolutionExplorer, ErrorList)
• Verify toolwindow_show returns supported names list for invalid input
• Verify toolwindow_hide closes tool windows by caption

Closes #4