feat(urgency): 通用紧急度通道（Declarer/Level + 只抬不压折算）+ IoT 首个生产者 + 她自己的结论走结构化标记穿透安静时段

internal/urgency/urgency_test.go

@@ -0,0 +1,41 @@
+package urgency
+
+import "testing"
+
+// zeroDeclarer 是一个未声明紧急度的生产者替身：它只实现契约本身。
+type zeroDeclarer struct{}
+
+func (zeroDeclarer) Urgency() Level { return LevelRoutine }
+
+// TestLevel_ZeroValueIsRoutine 钉住本通道的默认保守：未声明（零值）与显式声明
+// routine 同义，因此既有的、没标紧急度的事件生产者行为逐字不变。
+func TestLevel_ZeroValueIsRoutine(t *testing.T) {
+	t.Parallel()
+	var l Level
+	if l != LevelRoutine {
+		t.Fatalf("zero Level = %v, want %v", l, LevelRoutine)
+	}
+	var d Declarer = zeroDeclarer{}
+	if got := d.Urgency(); got != LevelRoutine {
+		t.Fatalf("undeclared urgency = %v, want %v", got, LevelRoutine)
+	}
+}
+
+// TestLevel_String 钉住标签稳定（日志、审计与思考记录依赖它）。
+func TestLevel_String(t *testing.T) {
+	t.Parallel()
+	cases := []struct {
+		in   Level
+		want string
+	}{
+		{in: LevelRoutine, want: "routine"},
+		{in: LevelWarning, want: "warning"},
+		{in: LevelCritical, want: "critical"},
+		{in: Level(7), want: "urgency(7)"},
+	}
+	for _, tc := range cases {
+		if got := tc.in.String(); got != tc.want {
+			t.Fatalf("Level(%d).String() = %q, want %q", int(tc.in), got, tc.want)
+		}
+	}
+}