fix: isolate headless Chrome profiles on macOS

[hesong12]

Summary

Every direct Chromium rendering path now launches with a unique temporary --user-data-dir; macOS additionally receives --use-mock-keychain.

This prevents headless document rendering from contending with the user's Chrome profile or attempting to create Chrome Safe Storage in the user login keychain, which can display a system Keychain reset prompt when HOME is isolated.

Coverage

The shared isolation helper is used by DOM dumping, regular screenshots, sized screenshots, and clipped screenshots. Temporary profiles are removed after the browser exits.

Validation

dotnet is not installed on the submitting macOS machine, so this needs the repository's .NET CI build.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Wait for timed-out Chrome processes before deleting profiles

When a Chrome invocation times out on Windows, both RunBinary and RunChromeCapture call Kill(true) and return without waiting for the process tree to exit. Dispose therefore immediately attempts this deletion while Chrome can still hold profile files open; the exception is swallowed and the unique officecli-chrome-* directory is permanently left behind, potentially leaking substantial temporary data after repeated render timeouts. Wait for termination or retry cleanup before abandoning the directory.

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