fix(core): normalize line endings in diff context snippets

Author: mikemikimike

packages/core/src/tools/diff-utils.test.ts

@@ -74,4 +74,13 @@ describe('getDiffContextSnippet', () => {
       '...\n9\nchanged\n11\n...',
     );
   });
+
+  it('should keep line indexes consistent for standalone CR line endings', () => {
+    const original = ['1', '2', '3', '4'].join('\r');
+    const modified = ['1', 'changed', '3', '4'].join('\r');
+
+    expect(getDiffContextSnippet(original, modified, 1)).toBe(
+      '1\nchanged\n3\n...',
+    );
+  });
 });

packages/core/src/tools/diff-utils.ts

@@ -23,7 +23,7 @@ export function getDiffContextSnippet(
   const normalizedOriginal = originalContent.replace(/\r\n?/g, '\n');
   const normalizedNew = newContent.replace(/\r\n?/g, '\n');
   const changes = Diff.diffLines(normalizedOriginal, normalizedNew);
-  const newLines = newContent.split(/\r?\n/);
+  const newLines = normalizedNew.split('\n');
   const ranges: Array<{ start: number; end: number }> = [];
   let newLineIdx = 0;