Proposal: progress reporting (analogue to FastMCP)

Is your feature request related to a problem? Please describe.
For long running requests, I understand clients can provide a progress token - this can be used to notify about progress.
I'd like to see a convenience method as part of e.g. a tool to provide updates on progress, e.g. for larger up- and downloads.

Describe the solution you'd like
In FastMCP there's a way to do this with very convenient DX (see description: https://gofastmcp.com/servers/progress#progress-reporting) - essentially providing the current state and an optional total value in a function and updating it.

Describe alternatives you've considered
I've seen there's a notify func but I'm not sure if this covers what I need.

Additional context
As stated above, this is about long running requests (e.g. a download or upload of a larger file, processing many items etc.)

Start by comparing the FastMCP progress-reporting description linked in the issue with the Go SDK's existing notify function. Identify the appropriate server or client entry point and define the intended convenience API for current progress and an optional total; done should include coverage for long-running requests such as uploads, downloads, or item processing. No implementation files or tests are named.