chore: remove custom contains helpers, drop unnecessary comment

.tool-versions

@@ -0,0 +1 @@
+golang 1.26.4

agent_test.go

@@ -35,7 +35,7 @@ func TestChannelMsgSerialization(t *testing.T) {
 	s := string(data)
 	checks := []string{"agent:123", "phx_join", "token", "test"}
 	for _, c := range checks {
-		if !contains(s, c) {
+		if !strings.Contains(s, c) {
 			t.Errorf("expected %q in JSON output %q", c, s)
 		}
 	}
@@ -69,19 +69,6 @@ func TestChannelMsgNullRef(t *testing.T) {
 	}
 }
 
-func contains(s, substr string) bool {
-	return len(s) >= len(substr) && searchString(s, substr)
-}
-
-func searchString(s, substr string) bool {
-	for i := 0; i <= len(s)-len(substr); i++ {
-		if s[i:i+len(substr)] == substr {
-			return true
-		}
-	}
-	return false
-}
-
 func testPools(t *testing.T) *jobPools {
 	t.Helper()
 	p := &jobPools{

mikrotik_test.go

@@ -660,24 +660,11 @@ func TestReadWordExceedsMaxSize(t *testing.T) {
 	if err == nil {
 		t.Error("expected error for word exceeding max size")
 	}
-	if !containsStr(err.Error(), "exceeds max") {
+	if !strings.Contains(err.Error(), "exceeds max") {
 		t.Errorf("expected 'exceeds max' in error, got: %v", err)
 	}
 }
 
-func containsStr(s, sub string) bool {
-	return len(s) >= len(sub) && searchStr(s, sub)
-}
-
-func searchStr(s, sub string) bool {
-	for i := 0; i <= len(s)-len(sub); i++ {
-		if s[i:i+len(sub)] == sub {
-			return true
-		}
-	}
-	return false
-}
-
 func TestReadSentenceError(t *testing.T) {
 	// Buffer with valid length byte but truncated word data
 	buf := bytes.NewBuffer([]byte{0x03, 'a'}) // length=3 but only 1 byte of data

update.go

@@ -85,7 +85,7 @@ func selfUpdate(downloadURL, expectedChecksum string) error {
 		return fmt.Errorf("create temp: %w", err)
 	}
 	tempPath := tempFile.Name()
-	defer func() { _ = os.Remove(tempPath) }() // cleanup on any failure
+	defer func() { _ = os.Remove(tempPath) }()
 
 	if _, err := tempFile.Write(body); err != nil {
 		_ = tempFile.Close()