[WIP] Add USB formatting dry-run validation

[Claude]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>USB formatting dry-run validation</issue_title>
<issue_description>### Crate / Stack Scope
Safe toolkit verification gate.

Definition of Done (DoD)

BootForge creator can perform a complete mock USB build, printing step logs, mock file extraction signatures, and verified folder checks without rewriting physical local partitions.

Validation Commands

python usb_creator.py --create C:\Users\Bobby\.gemini\antigravity\scratch\phoenixcore\downloads --dry-run

Blocked-by Dependencies

Issue 4.1, Issue 4.2, Issue 4.3

Safety Notes

[!WARNING]
Absolutely DO NOT execute partition format commands on real hosts during automation.

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Blocked-by / Epic Reference: #79</issue_description>

Comments on the Issue (you are @claude[agent] in this section)