test: 补充单元测试覆盖率 29.9% → 36.6%

新建 18 个测试文件，追加 30 个已有测试文件，覆盖协议解析、
错误分类、CEL 表达式求值、YAML 反序列化、字节编码等纯函数。

core/adaptive_pool_test.go

@@ -1,6 +1,7 @@
 package core
 
 import (
+	"sync/atomic"
 	"testing"
 	"time"
 )
@@ -152,3 +153,121 @@ func TestAdaptivePool_Wait(t *testing.T) {
 
 	t.Logf("Wait 测试通过: %v", duration)
 }
+
+// =============================================================================
+// maybeReduceTarget 补充覆盖
+// =============================================================================
+
+// TestMaybeReduceTarget_NoOpWhenRTTLow rttRatio <= 3.0 时不修改 target
+func TestMaybeReduceTarget_NoOpWhenRTTLow(t *testing.T) {
+	metrics := &ScanMetrics{}
+	pool, err := NewAdaptivePool(100, 100, func(interface{}) {}, metrics)
+	if err != nil {
+		t.Fatalf("创建线程池失败: %v", err)
+	}
+	defer pool.Release()
+
+	initialTarget := atomic.LoadInt32(&pool.target)
+
+	// RTTRatio 样本不足（< 20）返回 1.0，远低于 3.0 阈值
+	pool.maybeReduceTarget()
+
+	afterTarget := atomic.LoadInt32(&pool.target)
+	if afterTarget != initialTarget {
+		t.Errorf("rttRatio <= 3.0 时 target 不应改变: %d -> %d", initialTarget, afterTarget)
+	}
+}
+
+// TestMaybeReduceTarget_ReducesWhenRTTHigh rttRatio > 3.0 时压低 target 10%
+func TestMaybeReduceTarget_ReducesWhenRTTHigh(t *testing.T) {
+	metrics := &ScanMetrics{}
+	pool, err := NewAdaptivePool(200, 200, func(interface{}) {}, metrics)
+	if err != nil {
+		t.Fatalf("创建线程池失败: %v", err)
+	}
+	defer pool.Release()
+
+	// 伪造 RTT：让 fastEMA >> slowEMA，ratio > 3.0
+	// 方法：先用大 RTT 建立 fastEMA，再用小 RTT 建立 slowEMA
+	// 更直接：直接操作 atomic 字段（包内测试可以访问）
+	for i := 0; i < 25; i++ {
+		metrics.RecordConnect(10 * time.Millisecond) // 先建 baseline
+	}
+	// 现在把 fastEMA 人为拉高（写入一个远大于 slowEMA 的值）
+	pool.metrics.rttFastNs.Store(int64(400 * time.Millisecond))
+	pool.metrics.rttSlowNs.Store(int64(10 * time.Millisecond))
+
+	initialTarget := atomic.LoadInt32(&pool.target)
+
+	pool.maybeReduceTarget()
+
+	afterTarget := atomic.LoadInt32(&pool.target)
+	if afterTarget >= initialTarget {
+		t.Errorf("rttRatio > 3.0 时 target 应被压低: %d -> %d", initialTarget, afterTarget)
+	}
+
+	// 验证是 ×0.9
+	expected := int32(float64(initialTarget) * 0.9)
+	if afterTarget != expected {
+		t.Errorf("target 应为 %d (×0.9), 实际 %d", expected, afterTarget)
+	}
+}
+
+// TestMaybeReduceTarget_ClampToMinTarget target 压低后不低于 ceiling/5 或 10
+func TestMaybeReduceTarget_ClampToMinTarget(t *testing.T) {
+	metrics := &ScanMetrics{}
+	// ceiling=20, minTarget = max(20/5, 10) = 10
+	// target=10, newTarget = int(10*0.9) = 9 → 被 clamp 到 10 → newTarget == target → 不更新
+	pool, err := NewAdaptivePool(10, 20, func(interface{}) {}, metrics)
+	if err != nil {
+		t.Fatalf("创建线程池失败: %v", err)
+	}
+	defer pool.Release()
+
+	// 强制设置 target=10（初始值就是 10，但确认一下）
+	atomic.StoreInt32(&pool.target, 10)
+
+	// 伪造 rttRatio > 3.0
+	for i := 0; i < 25; i++ {
+		metrics.RecordConnect(10 * time.Millisecond)
+	}
+	pool.metrics.rttFastNs.Store(int64(400 * time.Millisecond))
+	pool.metrics.rttSlowNs.Store(int64(10 * time.Millisecond))
+
+	pool.maybeReduceTarget()
+
+	afterTarget := atomic.LoadInt32(&pool.target)
+	// newTarget=9 < minTarget=10 → clamp 到 10 → 10 == target → 不写入
+	if afterTarget != 10 {
+		t.Errorf("clamp 后 target 应保持 10, 实际 %d", afterTarget)
+	}
+}
+
+// TestMaybeReduceTarget_LargeCeilingMinTarget ceiling 足够大时 minTarget = ceiling/5
+func TestMaybeReduceTarget_LargeCeilingMinTarget(t *testing.T) {
+	metrics := &ScanMetrics{}
+	// ceiling=100, minTarget = 100/5 = 20
+	// target=21 → newTarget = int(21*0.9) = 18 → clamp 到 20
+	pool, err := NewAdaptivePool(21, 100, func(interface{}) {}, metrics)
+	if err != nil {
+		t.Fatalf("创建线程池失败: %v", err)
+	}
+	defer pool.Release()
+
+	atomic.StoreInt32(&pool.target, 21)
+	atomic.StoreInt32(&pool.ceiling, 100)
+
+	for i := 0; i < 25; i++ {
+		metrics.RecordConnect(10 * time.Millisecond)
+	}
+	pool.metrics.rttFastNs.Store(int64(400 * time.Millisecond))
+	pool.metrics.rttSlowNs.Store(int64(10 * time.Millisecond))
+
+	pool.maybeReduceTarget()
+
+	afterTarget := atomic.LoadInt32(&pool.target)
+	// newTarget=18 < minTarget=20 → store 20; 20 < 21 → 更新
+	if afterTarget != 20 {
+		t.Errorf("应 clamp 到 minTarget=20, 实际 %d", afterTarget)
+	}
+}