📝 align portable examples and release messaging

examples/file_rotation/main.mbt

@@ -1,19 +1,28 @@
 fn main {
   if !@lib.native_files_supported() {
-    println("native file sink is not available on this backend")
+    println("native file sink is not available on this backend; examples/presets stays portable, while file_rotation remains native-focused")
     return
   }
 
-  let logger = @lib.Logger::new(
-    @lib.file_sink(
-      "bitlogger-example.log",
-      auto_flush=true,
-      rotation=Some(@lib.file_rotation(128, max_backups=2)),
+  let logger = @lib.build_logger(
+    @lib.with_file_rotation(
+      @lib.file(
+        "bitlogger-example.log",
+        min_level=@lib.Level::Info,
+        target="demo.file",
+        auto_flush=true,
+      ) catch {
+        err => {
+          ignore(err)
+          println("invalid file preset config")
+          return
+        }
+      },
+      128,
+      max_backups=2,
     ),
-    min_level=@lib.Level::Info,
-    target="demo.file",
   )
   logger.info("file rotation ready", fields=[@lib.field("kind", "file")])
-  ignore(logger.sink.flush())
-  ignore(logger.sink.close())
+  ignore(logger.flush())
+  ignore(logger.file_close())
 }