all: apply modernisers

Signed-off-by: Ophestra <cat@gensokyo.uk>

hst/fs.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"reflect"
+	"strings"
 
 	"hakurei.app/check"
 )
@@ -78,17 +79,17 @@ type FSImplError struct{ Value FilesystemConfig }
 
 func (f FSImplError) Error() string {
 	implType := reflect.TypeOf(f.Value)
-	var name string
-	for implType != nil && implType.Kind() == reflect.Ptr {
-		name += "*"
+	var buf strings.Builder
+	for implType != nil && implType.Kind() == reflect.Pointer {
+		buf.WriteByte('*')
 		implType = implType.Elem()
 	}
 	if implType != nil {
-		name += implType.Name()
+		buf.WriteString(implType.Name())
 	} else {
-		name += "nil"
+		buf.WriteString("nil")
 	}
-	return fmt.Sprintf("implementation %s not supported", name)
+	return "implementation " + buf.String() + " not supported"
 }
 
 // FilesystemConfigJSON is the [json] adapter for [FilesystemConfig].