Feature: streaming pagination via Stream<Item = T> instead of eager collection

[ZialeHub]

Problem

Request::send() currently collects all pages into memory before returning. For large result sets (thousands of records) this:

• holds the entire dataset in memory at once
• cannot be cancelled mid-way through
• provides no progress feedback to the caller
• cannot be consumed lazily by a downstream pipeline

Proposed feature

Add a .stream() method on Request that returns a futures::Stream<Item = Result<T>>:

use futures::StreamExt;

let mut stream = api
    .get::<Vec<Resource>>("/resources")?
    .pagination(PaginationRule::OneShot)
    .stream(); // returns impl Stream<Item = Result<Vec<Resource>>>

while let Some(page) = stream.next().await {
    let records = page?;
    process(records).await;
}

Or with per-item streaming (flat-mapping pages):

let mut stream = api
    .get::<Resource>("/resources")?
    .stream_items(); // returns impl Stream<Item = Result<Resource>>

stream.for_each(|item| async move {
    println!("{:?}", item?);
}).await;

Design notes

• .stream() — yields one page (Vec<T>) per Poll::Ready, fetching the next page lazily on demand
• .stream_items() — flat-maps pages into individual items
• Both should respect the rate limiter between pages
• Cancellation is implicit: dropping the stream stops fetching further pages
• The existing .await (eager) behaviour is preserved unchanged

Dependencies

• futures or async-stream crate
• Compatible with all Pagination strategy types (page/offset/cursor)