fix: avoid leaking CheckedContinuations by removing possible Channel actor reentrancy

Sources/AsyncDataLoader/Channel.swift

@@ -0,0 +1,55 @@
+actor Channel<Success: Sendable, Failure: Error>: Sendable {
+    private var waiters = [Waiter<Success, Failure>]()
+    private var result: Result<Success, Failure>?
+}
+
+typealias Waiter<Success, Failure> = CheckedContinuation<Success, Error>
+
+extension Channel {
+    @discardableResult
+    func fulfill(_ success: Success) -> Bool {
+        guard result == nil else {
+            return true
+        }
+
+        result = .success(success)
+
+        while let waiter = waiters.popLast() {
+            waiter.resume(returning: success)
+        }
+
+        return false
+    }
+
+    @discardableResult
+    func fail(_ failure: Failure) -> Bool {
+        guard result == nil else {
+            return true
+        }
+
+        result = .failure(failure)
+
+        while let waiter = waiters.popLast() {
+            waiter.resume(throwing: failure)
+        }
+
+        return false
+    }
+
+    var value: Success {
+        get async throws {
+            try await withCheckedThrowingContinuation { continuation in
+                Task {
+                    switch result {
+                    case let .success(success):
+                        continuation.resume(returning: success)
+                    case let .failure(failure):
+                        continuation.resume(throwing: failure)
+                    case nil:
+                        waiters.append(continuation)
+                    }
+                }
+            }
+        }
+    }
+}