Count every reconnect in reconnect_count (closes #68)

`reconnect_count` in `/api/v1/stats` stayed 0 however often the stream reconnected: `SetConnected` counted a reconnect only while the stream was still marked connected, and the streamer always marks it disconnected first. It now counts one reconnect for every connection after the first, recognised by the zero `connectedSince` before the first connection. A test connects and disconnects twice and expects 2.

Model: opus-5-5

internal/metrics/metrics.go

@@ -60,17 +60,22 @@ func New() *Tracker {
 	}
 }
 
-// SetConnected updates the connection status
+// SetConnected updates the connection status. Every connection after the
+// first counts one reconnect.
 func (t *Tracker) SetConnected(connected bool) {
-	wasConnected := t.isConnected.Swap(connected)
-	if connected {
-		t.mu.Lock()
-		t.connectedSince = time.Now()
-		t.mu.Unlock()
-		// Increment reconnect count (but not for the initial connection)
-		if wasConnected || t.reconnectCount.Load() > 0 {
-			t.reconnectCount.Add(1)
-		}
+	t.isConnected.Store(connected)
+	if !connected {
+		return
+	}
+
+	t.mu.Lock()
+	// connectedSince is zero until the first connection.
+	connectedBefore := !t.connectedSince.IsZero()
+	t.connectedSince = time.Now()
+	t.mu.Unlock()
+
+	if connectedBefore {
+		t.reconnectCount.Add(1)
 	}
 }