Document multiple Workflow and Activity arguments across SDK guides

[brianstrauch]

Summary

• Update GreetingWorkflow examples in Go, Java, .NET, Ruby, Rust, and TypeScript to pass first and last names, matching the Python example.
• Put Python and Rust multi-argument guidance directly below the relevant code examples.
• Keep Rust's CLI-based starter and document its tuple input for SDK calls.

Validation

• rumdl fmt --check .
• rumdl check .
• skills-ref validate on a correctly named temporary skill directory
• git diff --check

Closes #70