ApproveWaiter.Resolve goroutine leak fix

[x2d7]

Summary

Fix for a goroutine leak in ApproveWaiter on context cancellation.

Fix: Goroutine leak on context cancellation (#44)

ApproveWaiter.Resolve spawns a goroutine via resolveSync when it can't immediately send a verdict. This goroutine blocks on a.verdicts <- verdict. If the context is cancelled before or during Wait, it exits without draining the channel — leaving the goroutine blocked indefinitely.

The fix stores the context in ApproveWaiter when Wait is called, and uses it in resolveSync to unblock on cancellation:

// before
func (a *ApproveWaiter) resolveSync(verdict Verdict) {
    a.verdicts <- verdict
}

// after
func (a *ApproveWaiter) resolveSync(verdict Verdict) {
    select {
    case a.verdicts <- verdict:
    case <-a.ctx.Done():
    }
}

Closes #44