Exercise 2: Two Steps Showing Both Halves of the Duality — Possible Solution
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EXAMPLE 1: STEP 1 — FIRST BOOT
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Elena spends time on the interface tour - the Dock, Menu Bar, Spotlight - which is entirely the proprietary GUI half of the duality: none of that is open-source or Unix-derived, it's Apple's own designed experience. In the same step, she opens Terminal and runs `uname -a`, seeing "Darwin" reported directly - proof of the certified Unix core running underneath that exact same GUI. One step, both halves shown side by side: the polished surface and the real Unix system directly beneath it.

EXAMPLE 2: STEP 4 — INSTALLING SOFTWARE
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Installing a Cask through Homebrew and then double-clicking it to launch is a GUI-level action reached through the proprietary App/Dock experience. But confirming its trustworthiness with `codesign -dv --verbose=4` and `spctl -a -vv` from Terminal directly exercises the cryptographic signing and Gatekeeper mechanisms that are the real, verifiable, non-cosmetic trust system underneath - again, a GUI-facing action backed directly by an inspectable, Unix-adjacent command-line verification step.

WHY THIS WORKS AS AN ANSWER
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It picks two genuinely distinct steps from Elena's session and, for each, explains specifically which action represents the proprietary-GUI half and which represents the certified-Unix-core half, showing that both halves are present and cooperating within the same step rather than existing as two separate, unrelated activities.