feat(desktop): unlock by sliding the vault doors open

[pyramation]

Summary

Unlocking is no longer a screen swap — it removes a physical barrier. The locked app is one sealed surface carrying the dcrypt mark across the seam; on unlock the surface splits down the middle and the halves slide off-screen, revealing the vault that was already rendered behind them. Locking runs it in reverse.

Three ideas make it work:

The mark tears in half for free. Each panel is w-1/2 overflow-hidden and contains a viewport-wide copy of the face, offset so the two copies compose one image:

<div className="absolute inset-y-0 w-1/2 overflow-hidden" style={{ transform: parted ? `translateX(${side === 'left' ? '-100%' : '100%'})` : 'translateX(0)' }}>
  <div className="absolute w-screen" style={{ left: side === 'left' ? 0 : '-50vw' }}>
    <Loader animate={working} />
  </div>
</div>

Sealed, it looks like one logo; parting, each door carries its own half.

The loader and the door are the same thing. Loader gained animate, so the mark assembles itself while Argon2id runs (the real 1–2 s wait) and rests as the finished stack otherwise — no spinner-then-transition. The separate full-screen busy view in UnlockScreen is gone; it is now just the controls that ride on the doors.

The vault is mounted before the doors move, which is what sells the reveal. App replaces unlocked: boolean with a phase:

type Phase = 'locked' | 'opening' | 'unlocked' | 'closing';
// vault mounted for every phase but 'locked'; doors present for every phase but 'unlocked'

opening → unlocked and closing → locked are committed by the doors' onRest. Locking fires vault.lock() concurrently with the animation, which the earlier snapshot-key work made cheap enough to hide entirely behind 380 ms.

Motion: 560 ms cubic-bezier(.2,.8,.2,1) open (measured deceleration 0 → −800 px), 380 ms closing with a slight overshoot past centre so it reads as a latch (measured: −283 → +10.6 → 0), inner-edge shadows only while travelling, and the vault settling scale(.985) → 1 behind. prefers-reduced-motion collapses all of it to a 120 ms cross-fade.

Testing

Measured both directions in the running app over CDP (transform samples above, frames in the webps). Desktop lint, 27 tests (including new doorDuration coverage) and build pass.

Link to Devin session: https://app.devin.ai/sessions/04636534e07048089ffb6b78142e12cd
Requested by: @pyramation

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