feat: add raw parameter to get_file_contents tool

[ko1ynnky]

Summary

Adds an optional raw boolean parameter to the get_file_contents tool to return plain text content instead of base64 encoded content, addressing issue #372.

Changes

• ✅ Added raw boolean parameter to get_file_contents tool schema
• ✅ When raw=true, fetches file content via GitHub's download URL and returns plain text
• ✅ When raw=false or unset, maintains existing base64 encoded behavior
• ✅ Returns appropriate error for directories when raw=true
• ✅ Handles files without download URLs gracefully
• ✅ Added comprehensive test coverage for edge cases

Benefits

• Reduces token consumption for LLM interactions by avoiding base64 decoding
• Improves model performance by providing direct access to file content
• Maintains backward compatibility with existing implementations
• Provides interface consistency with other tools like create_or_update_file

Test Coverage

• Schema validation includes raw parameter
• Directory handling with raw=true returns appropriate error
• Files without download URL return appropriate error
• All existing tests continue to pass

Example Usage

# Get base64 encoded content (existing behavior)
get_file_contents --owner github --repo docs --path README.md

# Get raw text content (new feature)  
get_file_contents --owner github --repo docs --path README.md --raw true

Closes #372

🤖 Generated with Claude Code

[SamMorrowDrums]

Thank you for the contribution. The file API just doesn't work well for this, so I've made this: #505

I'm going to close out this one in favour of mine, as I think it is simpler, and was much needed. 🙏