CheckedContinuation never resumed in NetworkTransport send/receive on actor dealloc (Swift 6.3)

[doozMen]

Bug

When NetworkTransport is deallocated while an async send(), sendHeartbeat(), or receiveData() operation is in-flight, the CheckedContinuation inside the NWConnection completion handler is never resumed — causing a permanent deadlock.

Root Cause

The .contentProcessed completion closures capture [weak self] but do not capture continuation directly. When self becomes nil in the completion handler, the guard let self else { return } exits without resuming the continuation.

This violates Swift's CheckedContinuation contract: a continuation must be resumed exactly once. Never resuming causes the caller to hang forever. In debug builds (Swift 6.3), this produces a runtime warning.

Affected Methods

• NetworkTransport.send(_ message: Data) — .contentProcessed completion
• NetworkTransport.sendHeartbeat() — .contentProcessed completion
• NetworkTransport.receiveData() — connection.receive completion (strong self capture inconsistency)

Reproduction

1. Create a NetworkTransport connection
2. Start a send() call
3. Deallocate the transport before the NWConnection completion fires
4. The caller hangs indefinitely

Environment

• Swift 6.3 (also affects earlier versions, but Swift 6.3 strict concurrency makes it more visible)
• Network framework (NWConnection)

Fix

Capture continuation directly in completion closures alongside [weak self], and resume with an error in the guard's else branch. See PR #213.

[doozMen]

Fixed in PR #213. The fix captures continuation directly in all NWConnection completion closures via [weak self, continuation] capture list, and resumes with an error when self is nil. This guarantees the CheckedContinuation contract (exactly-once resumption) even when the actor deallocates during in-flight operations.