refactor(instruction): remove default governance instruction and update related tests

internal/ai/runtime/instruction/assembler_test.go

@@ -26,19 +26,12 @@ func TestAssemblerRespectsProvidedSources(t *testing.T) {
 	}
 }
 
-func TestAssemblerUsesDefaultGovernanceInstruction(t *testing.T) {
+func TestAssemblerDoesNotInjectGovernanceInstructionWhenInputIsEmpty(t *testing.T) {
 	result := NewAssembler().Assemble(AssemblerInput{})
-	expectedSnippets := []string{
-		"禁止承诺未经系统确认的处理时效、完成时间、回访时间或联系时间。",
-		"禁止代表人工团队、技术团队、售后团队承诺后续动作",
-		"不能自行补充内部处理流程、SLA 或跟进安排。",
+	if result.Text != "" {
+		t.Fatalf("expected empty assembled text, got: %s", result.Text)
 	}
-	for _, snippet := range expectedSnippets {
-		if !strings.Contains(result.Text, snippet) {
-			t.Fatalf("missing governance snippet %q in assembled text: %s", snippet, result.Text)
-		}
-	}
-	if !result.Summary.HasGovernanceRule {
-		t.Fatalf("expected governance rule summary, got %#v", result.Summary)
+	if result.Summary.HasGovernanceRule {
+		t.Fatalf("expected no governance rule summary, got %#v", result.Summary)
 	}
 }