feat(tools): Add diagnostics tools

[CalvinAllen]

Description

Implement diagnostics-related MCP tools to allow AI assistants to access error lists and output windows.

Tools to Implement

• errors_list - Get errors, warnings, and messages from the Error List
• output_read - Read content from Output window panes
• output_write - Write to Output window panes

VS APIs

• DTE2.ToolWindows.ErrorList
• DTE2.ToolWindows.OutputWindow
• OutputWindowPane