Remove the relay's broker wait channel after each tick (closes #151)

The IRC relay registers a broker wait channel on each pass of its
loop, and when the 100 ms ticker fired instead of a notification it
looped without removing that channel. An idle IRC listener connection
added ten channels a second to the broker, and all but the last stayed
after the connection closed. The ticker case now removes its channel,
as the HTTP long-poll does after its timer.

Broker.ListenerCount returns how many wait channels a user holds, so
the test can check that an idle connection holds at most one, and
none after it closes.

Model: opus-5-5

internal/ircserver/relay_test.go

@@ -5,6 +5,9 @@ import (
 	"slices"
 	"strings"
 	"testing"
+	"time"
+
+	"sneak.berlin/go/neoirc/internal/ircserver"
 )
 
 // queueMessage queues a message for the user with nick
@@ -44,6 +47,51 @@ func (env *testEnv) queueMessage(
 	env.brk.Notify(sessionID)
 }
 
+// TestRelayKeepsOneWaitChannel checks that an idle IRC
+// listener connection holds at most one broker wait channel
+// across several relay ticks, and none once it closes.
+func TestRelayKeepsOneWaitChannel(t *testing.T) {
+	t.Parallel()
+
+	const idleTicks = 5
+
+	env := newTestEnv(t)
+
+	client := env.dial(t)
+	client.register("idle")
+
+	sessionID, err := env.database.GetSessionByNick(t.Context(), "idle")
+	if err != nil {
+		t.Fatalf("get session of idle: %v", err)
+	}
+
+	for tick := range idleTicks {
+		time.Sleep(ircserver.PollInterval)
+
+		got := env.brk.ListenerCount(sessionID)
+		if got > 1 {
+			t.Fatalf("tick %d: got %d wait channels, want at most 1",
+				tick+1, got)
+		}
+	}
+
+	err = client.conn.Close()
+	if err != nil {
+		t.Fatalf("close: %v", err)
+	}
+
+	deadline := time.Now().Add(testTimeout)
+
+	for env.brk.ListenerCount(sessionID) != 0 {
+		if time.Now().After(deadline) {
+			t.Fatalf("after close: got %d wait channels, want 0",
+				env.brk.ListenerCount(sessionID))
+		}
+
+		time.Sleep(relayCheckStep)
+	}
+}
+
 // TestRelayMultiLineBody checks that each line of a PRIVMSG
 // or NOTICE body sent over the HTTP API reaches an IRC
 // listener user as its own line.