Hits the Task 7.1 <=500 LOC gate for setup.ts by extracting the SetupStep
registry, the WizardState singleton, clearWizardState and finishSetup into a
sibling setup-steps.ts; setup.ts is now a thin shell (progress track + render
loop + boot + re-exports). The import is one-directional (setup -> setup-steps),
no cycle. Also restores the non-extension copy-vault-config-JSON escape hatch on
the done step (per product decision) while keeping the redundant register-device
button dropped (the SW handler registers the device).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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