Parse tool args from CLI as JsonValue instead of just strings

[olaservo]

Fix CLI argument parsing to support JSON values (resolves #431)

Motivation and Context

The CLI only accepted string arguments for tool calls, while the web UI supported full JSON values (objects, arrays, numbers, booleans). This made the CLI less useful for testing tools that require structured data.

How Has This Been Tested?

• CLI builds successfully without TypeScript errors
• Tested parsing of strings, numbers, booleans, objects, arrays, and null values
• Verified backward compatibility with existing string arguments
• Confirmed help command displays correctly

Breaking Changes

None. All existing CLI usage continues to work unchanged.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed