fix(coding): preserve contextual unicode folding

tests/unit/coding-project-files.test.ts

@@ -110,6 +110,7 @@ describe('PI-105 project file service', () => {
     await mkdir(path.join(root, 'node_modules', 'private-package'), { recursive: true });
     await writeFile(path.join(root, 'docs', 'guide.md'), 'First line\nNeedle and needle again\n', 'utf8');
     await writeFile(path.join(root, 'docs', 'unicode.md'), 'İx needle and NEEDLE\n', 'utf8');
+    await writeFile(path.join(root, 'docs', 'greek.md'), 'ΟΣ\n', 'utf8');
     await writeFile(path.join(root, 'node_modules', 'private-package', 'secret.txt'), 'needle\n', 'utf8');
     const service = new CodingProjectFileService({
       async run() {
@@ -145,5 +146,9 @@ describe('PI-105 project file service', () => {
         { text: 'NEEDLE', start: 14, end: 20 },
       ],
     }));
+    expect(await service.search(root, 'ος')).toContainEqual(expect.objectContaining({
+      path: 'docs/greek.md',
+      submatches: [{ text: 'ΟΣ', start: 0, end: 2 }],
+    }));
   });
 });