datastream/javascript/async

JavaScript-only async edge adapters.

The cross-target Stream(a) core is synchronous and pull-based: each pull either yields the next element immediately or reports Done. That contract keeps the core small and predictable across Erlang and JavaScript, but it also means a true JavaScript AsyncIterable(a) cannot be represented as a Stream(a) without buffering or polling.

The official boundary is therefore:

• async input stays in host JavaScript until it has been reduced to a bounded value or batch, then enters the core through the normal constructors (source.once, source.from_list, source.from_bit_array, source.resource, …);
• synchronous Stream(a) pipelines leave the core through to_async_iterable, which exposes them to for await ... of and other host-side async consumers.

This keeps the core honest about its synchronous pull contract while still giving JavaScript applications a first-party interop point.

pub const javascript_only_marker: String