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。

plugins/services/findnet_test.go

@@ -0,0 +1,183 @@
+//go:build plugin_findnet || !plugin_selective
+
+package services
+
+import (
+	"strings"
+	"testing"
+)
+
+// --- hexUnicodeToString ---
+
+func TestHexUnicodeToString(t *testing.T) {
+	p := NewFindNetPlugin()
+
+	cases := []struct {
+		name string
+		src  string
+		want string
+	}{
+		{
+			name: "empty string",
+			src:  "",
+			want: "",
+		},
+		{
+			name: "UTF-16LE TEST",
+			// T=0x54 E=0x45 S=0x53 T=0x54, LE pairs: 5400 4500 5300 5400
+			src:  "54004500530054",
+			want: "TEST",
+		},
+		{
+			name: "odd length gets padded to 4-multiple",
+			// 奇数长度补0至4的倍数："540045005300540" → "5400450053005400" → "TEST"
+			src:  "540045005300540", // 15 hex chars
+			want: "TEST",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := p.hexUnicodeToString(tc.src)
+			if got != tc.want {
+				t.Errorf("got %q, want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+// --- isValidHostname ---
+
+func TestIsValidHostname(t *testing.T) {
+	p := NewFindNetPlugin()
+
+	cases := []struct {
+		name  string
+		input string
+		want  bool
+	}{
+		{name: "empty", input: "", want: false},
+		{name: "valid hostname", input: "test-pc", want: true},
+		{name: "single char", input: "a", want: false}, // regex requires at least 2 chars (start+middle+end)
+		{name: "too long", input: strings.Repeat("a", 256), want: false},
+		{name: "valid alphanumeric", input: "PC01", want: true},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := p.isValidHostname(tc.input)
+			if got != tc.want {
+				t.Errorf("isValidHostname(%q) = %v, want %v", tc.input, got, tc.want)
+			}
+		})
+	}
+}
+
+// --- isValidNetworkAddress ---
+
+func TestIsValidNetworkAddress(t *testing.T) {
+	p := NewFindNetPlugin()
+
+	cases := []struct {
+		name  string
+		input string
+		want  bool
+	}{
+		{name: "IPv4", input: "192.168.1.1", want: true},
+		{name: "IPv6 loopback", input: "::1", want: true},
+		{name: "valid hostname fallback", input: "test-host", want: true},
+		{name: "invalid", input: "not_an_ip!!!", want: false},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := p.isValidNetworkAddress(tc.input)
+			if got != tc.want {
+				t.Errorf("isValidNetworkAddress(%q) = %v, want %v", tc.input, got, tc.want)
+			}
+		})
+	}
+}
+
+// --- cleanAndValidateAddress ---
+
+func TestCleanAndValidateAddress(t *testing.T) {
+	p := NewFindNetPlugin()
+
+	cases := []struct {
+		name string
+		data []byte
+		want string
+	}{
+		{
+			name: "valid IPv4 bytes",
+			data: []byte("192.168.1.100"),
+			want: "192.168.1.100",
+		},
+		{
+			name: "bytes with unprintable chars around valid IP",
+			data: append([]byte{0x00, 0x01}, append([]byte("10.0.0.1"), 0x00)...),
+			want: "10.0.0.1",
+		},
+		{
+			name: "invalid data returns empty",
+			data: []byte{0x00, 0x01, 0x02, 0x03},
+			want: "",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := p.cleanAndValidateAddress(tc.data)
+			if got != tc.want {
+				t.Errorf("got %q, want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+// --- NetworkInfo.Summary ---
+
+func TestNetworkInfoSummary(t *testing.T) {
+	t.Run("invalid returns discovery failed text", func(t *testing.T) {
+		ni := &NetworkInfo{Valid: false}
+		got := ni.Summary()
+		if got == "" {
+			t.Error("expected non-empty text for invalid NetworkInfo")
+		}
+		// 内容是 i18n key，只验证非空即可
+	})
+
+	t.Run("valid with hostname and IPv4", func(t *testing.T) {
+		ni := &NetworkInfo{
+			Valid:     true,
+			Hostname:  "PC01",
+			IPv4Addrs: []string{"192.168.1.1", "10.0.0.1"},
+		}
+		got := ni.Summary()
+		if got == "" {
+			t.Error("expected non-empty summary")
+		}
+	})
+}
+
+// --- parseNetworkInfo ---
+
+func TestParseNetworkInfo(t *testing.T) {
+	p := NewFindNetPlugin()
+
+	t.Run("empty data returns invalid", func(t *testing.T) {
+		info := p.parseNetworkInfo([]byte{})
+		if info.Valid {
+			t.Error("expected Valid=false for empty data")
+		}
+	})
+
+	t.Run("data without valid hostname or IP returns invalid", func(t *testing.T) {
+		// 全零数据，hostname 解析出空字符串，不会 Valid
+		info := p.parseNetworkInfo(make([]byte, 64))
+		if info.Valid {
+			t.Error("expected Valid=false for zero data")
+		}
+	})
+}