Expose transport capability expectations for the 0.5.0 data plane

[bbopen]

Expose transport capability expectations for the 0.5.0 data plane so Node, Pyodide, and HTTP support boundaries stay easy to understand.

Acceptance Criteria

• runtime and docs make clear which transports support which data-plane features
• HTTP and Pyodide boundaries stay explicit where Tywrap intentionally does not own the lifecycle or transport path
• examples and docs avoid implying unsupported transport capabilities