feat(mpsc): add fair capacity reservations to bounded channels

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 
 ## Unreleased
 
+### New features
+
+* Add bounded MPSC `reserve` and `try_reserve` methods returning a `Permit`, allowing callers to wait for capacity before constructing a message; pending sends and reservations receive capacity in wait-queue order, and unused permits release capacity without claiming message order.
+
 ### Bug fixes
 
 * Release MPSC receiver wakers when the receiver is dropped, avoiding retained tasks and ownership cycles when a waker holds a sender.
@@ -13,7 +17,6 @@ All notable changes to this project will be documented in this file.
 ### Improvements
 
 * Finish releasing buffered bounded MPSC messages even if one message destructor panics.
-* Reduce bounded MPSC contention when senders or the receiver are not waiting, improving throughput without changing capacity or cancellation semantics.
 * Improve unbounded MPSC throughput with batched receiving and incremental storage reclamation; empty-buffer retention is bounded independently of previous peak occupancy.
 
 ## v0.7.2

LICENSE

@@ -377,18 +377,6 @@ the Apache-2.0 option for the incorporated portions.
 Asyncband does not provide the upstream crate's synchronized receive
 operations and simplifies the incorporated implementation accordingly.
 
-Portions of asyncband/src/internal/atomic_waker.rs are derived from futures-rs
-0.3.34 at the following exact revision and source path:
-
-  https://github.com/rust-lang/futures-rs/blob/705e6b5c0f06535b1aac1cb1989a172b3d45be8c/futures-core/src/task/__internal/atomic_waker.rs
-
-futures-rs is licensed under Apache-2.0 or MIT. Apache Asyncband uses the
-Apache-2.0 option for the incorporated portions. The upstream source carries
-the following copyright notices:
-
-  Copyright (c) 2016 Alex Crichton
-  Copyright (c) 2017 The Tokio Authors
-
 The polling loop in asyncband/src/blocking/executor.rs is adapted from Pollster
 1.0.1 at the following exact revision and source path: