test(search): send real CSI CUP in #3834 null-char case

The integration test intended to move the cursor forward with ESC [ C
but wrote the literal string \x1b[C due to double escaping. Use a
single-escaped '\x1b[CHi Hi' so the terminal receives the control
sequence and creates the null cell the scenario describes.

Co-authored-by: Cursor <cursoragent@cursor.com>

addons/addon-search/test/SearchAddon.test.ts

@@ -501,7 +501,7 @@ test.describe('Search Tests', () => {
         window.search.onDidChangeResults(e => window.calls.push(e));
       `);
       // Move cursor forward 1 time to create a null character, as opposed to regular whitespace
-      await ctx.proxy.write('\\x1b[CHi Hi');
+      await ctx.proxy.write('\x1b[CHi Hi');
       strictEqual(await ctx.page.evaluate(`window.search.findPrevious('h', { decorations: { activeMatchColorOverviewRuler: '#ff0000' } })`), true);
       deepStrictEqual(await ctx.page.evaluate('window.calls'), [
         { resultCount: 2, resultIndex: 1 }