web: hide native number spinners; slower, fully staggered rounds

Per Justin: the native number-input spinners rendered as light boxes on
the dark theme, so they are gone app-wide (typing and arrow keys keep
working). Playback pacing: rounds now take 1000 ms at 1x, appearance
moments spread across 95% of the interval via a murmur3-style
full-avalanche hash, and each dot fades over 30% of the interval, so a
round reads as a continuous trickle instead of a flash.

web/src/assets/main.css

@@ -72,6 +72,19 @@ button {
   font-family: inherit;
 }
 
+/* The native number-input spinners render as light boxes that clash with
+   the dark theme and crowd the compact fields; arrow keys and typing keep
+   working without them. */
+input[type='number'] {
+  appearance: textfield;
+}
+
+input[type='number']::-webkit-outer-spin-button,
+input[type='number']::-webkit-inner-spin-button {
+  appearance: none;
+  margin: 0;
+}
+
 .visually-hidden {
   position: absolute;
   width: 1px;

web/src/components/NetworkView.vue

@@ -75,7 +75,7 @@ function onNodeClick(nodeIndex: number, event: MouseEvent) {
 // the panel stats), then fade in over the rest of the interval; playback
 // never shows a finished still frame between rounds.
 const roundIntervalMs = computed(() => ROUND_MS / store.state.speed)
-const popDurationMs = computed(() => roundIntervalMs.value * (1 - APPEAR_WINDOW) + 120)
+const popDurationMs = computed(() => roundIntervalMs.value * 0.3)
 
 function popDelay(nodeIndex: number): string {
   return `${appearanceJitter(nodeIndex) * APPEAR_WINDOW * roundIntervalMs.value}ms`

web/src/composables/usePlayback.ts

@@ -6,8 +6,8 @@ import { useSimStore, type SimStore } from './useSimStore'
 // one-time autoplay). Playback never loops; at the final round the play
 // button becomes a replay affordance.
 
-export const ROUND_MS = 700
+export const ROUND_MS = 1000
-export const REDUCED_MOTION_ROUND_MS = 1000
+export const REDUCED_MOTION_ROUND_MS = 1200
 
 const SPEED_CYCLE: Record<number, 0.5 | 1 | 2> = { 0.5: 1, 1: 2, 2: 0.5 }
 

web/src/lib/reach.ts

@@ -1,5 +1,3 @@
-import { mulberry32 } from './mulberry32'
-
 // Cumulative reach at a playback round, shared by the panel stats and the
 // reach chart so both always agree with the network picture.
 export function reachedCountAtRound(reachedAtRound: number[], round: number): number {
@@ -12,10 +10,19 @@ export function reachedCountAtRound(reachedAtRound: number[], round: number): nu
 // jitter drives the dot's animation-delay and the live counter, so the
 // percentage ticks up exactly as dots start appearing.
 
-export const APPEAR_WINDOW = 0.7
+export const APPEAR_WINDOW = 0.95
 
+// A full-avalanche integer hash (murmur3 finalizer): consecutive node
+// indices land anywhere in [0, 1), so the appearance moments of a round's
+// nodes are spread evenly instead of clustering into one flash.
 export function appearanceJitter(nodeIndex: number): number {
-  return mulberry32(nodeIndex * 7919 + 17)()
+  let mixed = Math.imul(nodeIndex + 1, 0x9e3779b1)
+  mixed ^= mixed >>> 16
+  mixed = Math.imul(mixed, 0x85ebca6b)
+  mixed ^= mixed >>> 13
+  mixed = Math.imul(mixed, 0xc2b2ae35)
+  mixed ^= mixed >>> 16
+  return (mixed >>> 0) / 4294967296
 }
 
 // Reach as displayed mid-transition: every earlier round fully, plus the