- page.tsx: server component validates JWT + one-time-use before rendering any UI
- Three error states (expired/used/invalid) show static pages with no canvas
- SigningPageClientWrapper: dynamic import (ssr:false) for react-pdf browser requirement
- SigningPageClient: full-scroll PDF viewer with pulsing blue field overlays
- Field overlay coordinates convert PDF user-space (bottom-left) to screen (top-left)
- SigningProgressBar: sticky bottom bar with X/Y count + jump-to-next + submit button
- api/sign/[token]/pdf: token-authenticated PDF streaming route (no agent auth)
