fix(release): install probe script dependencies

[drewstone]

The protected one-shot model probe failed before any network request because its script imports proof tools from the workflow checkout, but the workflow installed dependencies only in the nested candidate checkout. Install the workflow checkout dependencies first. The candidate source and exact archive checks remain unchanged.

Validation: actionlint .github/workflows/release-model-probe.yml and git diff --check pass. A local script invocation now reaches PROTECTED_CONFIGURATION_REQUIRED with an intentionally empty environment, proving imports resolve before credentials or task admission. Probe run 36558344764 had zero admitted model requests.

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[tangletools]

✅ Auto-approved PR — 65eb50d3

Blanket team auto-approval is intentional. The merge gates are CI and codex-p1.
No automated review runs on this PR. This approval rests on the rule above alone.

_{tangletools · auto-approval · reason: blanket_auto_approve · 2026-09-29T11:02:11Z}