Smarter approach to the cookies (#103)

* Smarter approach to the cookies

  - Single maxCookieSize = 1400 constant with clear documentation
  - Combined cookie storage for ~40-45% size reduction
  - Backward compatible migration from legacy cookies

* Tuneup the code.

main_goroutine_leak_test.go

@@ -13,9 +13,9 @@ import (
 func TestGoroutineLeakPrevention_ContextCancellation(t *testing.T) {
 	tests := []struct {
 		name          string
-		cancelAfter   time.Duration
-		expectedLeaks int // Maximum expected goroutines after cleanup
 		description   string
+		cancelAfter   time.Duration
+		expectedLeaks int
 	}{
 		{
 			name:          "immediate_cancellation",