fix: reformat agent-shell testHelper.ts to pass prettier check

[Copilot]

The build_ts CI job was failing because test/testHelper.ts in agent-shell failed the prettier formatting check — a newly added waitFor call exceeded the line length limit.

Change

Reformatted the object argument in scrollContainer.waitFor() to multi-line style:

// Before
await scrollContainer.waitFor({ timeout: 120000, state: "attached" });

// After
await scrollContainer.waitFor({
    timeout: 120000,
    state: "attached",
});

Original prompt

Fix the failing GitHub Actions workflow build_ts (macos-latest, 22)
Analyze the workflow logs, identify the root cause of the failure, and implement a fix.
Job ID: 68274110387
Job URL: https://github.com/microsoft/TypeAgent/actions/runs/23464662092/job/68274110387

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