refactor: mdraid comments and organization

also hide serial / firmware in smart details if empty, remove a few
unnecessary ops, and add a few more passed state values

agent/fs_utils.go

@@ -0,0 +1,41 @@
+package agent
+
+import (
+	"os"
+	"strconv"
+	"strings"
+)
+
+// readStringFile returns trimmed file contents or empty string on error.
+func readStringFile(path string) string {
+	content, _ := readStringFileOK(path)
+	return content
+}
+
+// readStringFileOK returns trimmed file contents and read success.
+func readStringFileOK(path string) (string, bool) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return "", false
+	}
+	return strings.TrimSpace(string(b)), true
+}
+
+// fileExists reports whether the given path exists.
+func fileExists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}
+
+// readUintFile parses a decimal uint64 value from a file.
+func readUintFile(path string) (uint64, bool) {
+	raw, ok := readStringFileOK(path)
+	if !ok {
+		return 0, false
+	}
+	parsed, err := strconv.ParseUint(raw, 10, 64)
+	if err != nil {
+		return 0, false
+	}
+	return parsed, true
+}