test(zero-swift): report what the server saw when a mid-frame reconnect never opens (#109)

On the iOS Simulator the client's reconnect after a cut-off frame stopped
at "Connecting to …" for 10 s. The failure now lists when the server got
each upgrade request and answered it, so it shows whether the request
never came or the client never took the answer.

Amp-Thread-ID: https://ampcode.com/threads/T-c513a037-a257-45e0-b9a9-15c15edfe859

Co-authored-by: Amp <amp@ampcode.com>

Author: tmm

swift/Tests/E2ETests/TransportProbeTests.swift

@@ -227,12 +227,22 @@ struct TransportProbeTests {
   func clientReconnectsAfterTheServerGoesAwayMidFrame(_ kind: TransportKind) async throws {
     for binary in [false, true] {
       let connections = Box(0)
+      // What the server saw, in ms from the start, so that a reconnect that never opens shows whether the server answered its handshake.
+      let start = ContinuousClock.now
+      let seen = Box<[String]>([])
+      let saw: @Sendable (String) -> Void = { event in
+        let ms = (ContinuousClock.now - start) / .milliseconds(1)
+        seen.withLock { $0.append("\(event) at \(Int(ms)) ms") }
+      }
       let server = try await ScriptedServer { c in
         let n = connections.withLock {
           $0 += 1
           return $0
         }
-        await c.write(c.accept() + ScriptedServer.text(#"["connected",{"wsid":"w\#(n)"}]"#))
+        saw("connection \(n) upgrade request")
+        let upgrade = c.accept()
+        await c.write(upgrade + ScriptedServer.text(#"["connected",{"wsid":"w\#(n)"}]"#))
+        saw("connection \(n) answered")
         if n == 1 {
           try? await Task.sleep(for: .milliseconds(300))
           let row =
@@ -265,6 +275,7 @@ struct TransportProbeTests {
         "[probe] \(kind) client, server gone mid-\(binary ? "binary" : "text") frame: reconnected \(reconnected), states \(states), \(zero.connection.state)"
       )
       if !reconnected {
+        print("[probe]   server: \(seen.withLock { $0 })")
         for line in logs.all.suffix(8) { print("[probe]   \(line.prefix(300))") }
       }
       #expect(reconnected, "binary \(binary): \(zero.connection.state)")