fix: pass fixed uuid to toHtml in Styler.hide test to prevent flaky failures

The auto-generated table id (tsb-<random base-36>) could randomly contain
"r0" or "r1", causing the not.toContain assertions to fail intermittently
(~1% of runs). Passing a fixed uuid "x" makes the test deterministic.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

tests/stats/style.test.ts

@@ -391,7 +391,7 @@ describe("Styler.setCaption", () => {
 describe("Styler.hide", () => {
   test("hide index removes index column", () => {
     const df = makeNumericDf();
-    const html = dataFrameStyle(df).hide(0).toHtml();
+    const html = dataFrameStyle(df).hide(0).toHtml("x");
     expect(html).not.toContain("r0");
     expect(html).not.toContain("r1");
   });