Add article on MCP tools

[cpsievert]

Closes #111

[Copilot]

Pull Request Overview

This PR introduces comprehensive documentation for integrating and using Model Context Protocol (MCP) tools in Chatlas, fixes a broken link in the system prompt guide, and registers the new page in the site configuration.

• Added a new mcp-tools.qmd article covering installation, basic usage patterns (HTTP and stdio), and advanced examples with code execution.
• Corrected the RAG link path in the system prompt documentation.
• Updated _quarto.yml to include the new MCP tools guide in the site navigation.

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
docs/misc/mcp-tools.qmd	Added a full guide on setting up and using MCP tools
docs/get-started/system-prompt.qmd	Updated RAG link target to the correct file location
docs/_quarto.yml	Registered new MCP tools documentation page

Comments suppressed due to low confidence (1)

docs/misc/mcp-tools.qmd:130

• [nitpick] Consider clarifying why the example uses a negative argument (y=-3) for subtraction, or adjust to add(x=5, y=3) with a separate subtraction example to improve clarity.

add(x=5, y=-3)