test: fix flaky partials tests missing waitForNavigation()

[SisyphusZheng]

Problem

Two tests in packages/fresh/tests/partials_test.tsx are marked ignore: true due to flakiness:

• Line 1416: "opt out of partial navigation"
• Line 1482: "opt out of partial navigation Caching of JIT JS bundles #2"

Root Cause

Both tests click links with f-client-nav={false} (full navigation), but don't wait for the navigation to complete:

// Flaky (no navigation wait)
await page.locator(".update").click();
await page.locator(".done").wait();

// Correct (line 1592, non-flaky equivalent)
await Promise.all([
    page.waitForNavigation(),
    page.locator(".update").click(),
]);

The third test ("opt out of partial navigation in island") uses Promise.all([waitForNavigation(), click]) and is NOT marked flaky — confirming the root cause.

Fix

Wrap the click in Promise.all([page.waitForNavigation(), click()]) like the working test.