Add 150 UI and page state stickers in three pending sections

404s, loaders, success, errors, empty states, confirmation, under
construction, offline and more: 50 monochrome (ui), 50 colored (uicolor)
and 50 with an anime girl (uianime), on /test until approved.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

gen/ui/404/signpost.js

@@ -0,0 +1,20 @@
+// a signpost whose arrow boards keep swinging round to point every which way, while a question mark bobs on top
+const{sin,cos,PI,min,max}=Math,T=2*PI
+export const frames=24,delay=70
+const bk=u=>(u=min(1,max(0,u)),1+2.7*(u-1)**3+1.7*(u-1)**2)
+const B=[[112,94,0,-.12,[[.02,1],[.5,1]]],[154,82,PI,.1,[[.18,2],[.66,-2]]],[196,90,0,-.05,[[.34,1],[.84,1]]]]
+export default(c,t)=>{
+  const bs=B.map(([y,L,b,tl,S])=>[y,L,b+S.reduce((a,[t0,n])=>a+n*PI*bk((t-t0)/.14),0),tl])
+  const board=([y,L,a,tl])=>{
+    const k=cos(a),P=[[-14,-16],[L-22,-16],[L,0],[L-22,16],[-14,16]]
+    c.lineWidth=7;c.beginPath();for(const[u,v]of P)c.lineTo(128+u*k,y+v+u*k*tl);c.closePath();c.fill();c.stroke()
+    c.lineWidth=4;c.beginPath();c.moveTo(128+16*k,y+16*k*tl);c.lineTo(128+(L-34)*k,y+(L-34)*k*tl);c.stroke()
+  }
+  c.beginPath();c.roundRect(52,214,152,24,12);c.fill();c.stroke()
+  for(const b of bs)if(sin(b[2])<0)board(b)
+  c.lineWidth=7;c.beginPath();c.roundRect(118,86,20,140,6);c.fill();c.stroke()
+  for(const b of bs)if(sin(b[2])>=0)board(b)
+  c.save();c.translate(128,50+5*sin(T*t*2));c.rotate(.18*sin(T*t));c.scale(.88,.88)
+  for(const[w,st]of[[24,'#111'],[11,'#fff']])c.lineWidth=w,c.strokeStyle=st,c.beginPath(),c.arc(0,-12,12,PI,PI*2.3),c.quadraticCurveTo(0,2,0,8),c.stroke()
+  c.lineWidth=6;c.strokeStyle='#111';c.beginPath();c.arc(0,24,7,0,T);c.fill();c.stroke();c.restore()
+}