404: "Page Fault" — a SIGSEGV/memory-fault framing distinct from the
retired terminal easter egg, still fitting the CS-flavored identity.
Plain/unstyled for now like the rest of the placeholder layout;
restyle once the design system lands.
src/lib/spring.ts: a small CSS+Web Animations API spring utility
(damped harmonic oscillator -> keyframe progress values), per the
locked "no animation library" decision. Not wired into any component
yet — this is the foundational primitive the design system's motion
work will build on, kept free of any visual/component opinions.
