fix(app): preserve file line endings and UTF-8 BOM (#2277)

* fix(app): preserve file line endings and UTF-8 BOM

* refactor(app): simplify line ending preservation

Let the editor parse newline variants and serialize with the file's first separator. Mixed-ending files become uniform on edit without a separate normalization layer.

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Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>

packages/app/src/file-explorer/read-result.ts

@@ -8,8 +8,13 @@ export function explorerFileFromReadResult(file: FileReadResult): ExplorerFile {
     kind: file.kind,
     encoding: isText ? "utf-8" : "none",
     content: isText ? new TextDecoder().decode(file.bytes) : undefined,
+    hasBom: isText && hasUtf8Bom(file.bytes),
     mimeType: file.mime,
     size: file.size,
     modifiedAt: file.modifiedAt,
   };
 }
+
+function hasUtf8Bom(bytes: Uint8Array): boolean {
+  return bytes.length >= 3 && bytes[0] === 0xef && bytes[1] === 0xbb && bytes[2] === 0xbf;
+}