/// Shared accumulation-buffer helpers for `windowing` and `rate`.
/// Stream combining operators: `merge` and `concat`.
/// Concurrent processing operators: `rparallel` and `rfan_out`.
/// Trailing-edge rate-limiting operators: `rdebounce`, `rdebounce_batch`, `rthrottle`.
/// Transformation operators: `rmap`, `rfilter`, `rtap`, and `rreduce`.
/// Leading-edge windowing operators: `rbatch`, `rsliding_window`, `rtumbling_window`.