Optimize MCP & rule docs

[tembo]

Summary

Condensed documentation in mcp-servers.mdx and rule-files.mdx to reduce word count while preserving meaning:

• Converted verbose paragraphs to concise bullet points with em-dash formatting
• Streamlined Best Practices section from 4 paragraphs to 4 bullet points
• Simplified Troubleshooting from 5 paragraphs to 3 bullet points with question format
• Restructured What to Include section from 8 subsections to 2 grouped lists (Essential/Optional)
• Reduced overall verbosity by ~40% without losing key information

Want tembo to make any changes? Add a review or comment with @tembo and i'll get back to work!

[tembo]

Requesting review from @ryw who has experience with the following files modified in this PR:

• features/rule-files.mdx
• features/mcp-servers.mdx