fix: correct numeric types in progress notifications

[jamadeo]

The standard says:

The progress and the total values MAY be floating point.

https://modelcontextprotocol.io/specification/2025-06-18/basic/utilities/progress#progress-flow

Motivation and Context

Aligns with the standard

How Has This Been Tested?

Ran with a FastMCP server that looks like

@mcp.tool()
async def count(ctx: Context, until: int) -> int:
    """Counts and streams results"""
    for i in range(1, until + 1):
        await ctx.report_progress(i, until)
        await asyncio.sleep(0.5)

    return until

Breaking Changes

Yes, this changes they type of a public field of a struct.

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

Additional context