feat: animate the event slide with clickable step controls

On slide entry, reveal the typed fields first, then flash in the hashed
`id` and signed `sig` (~0.9s apart) while the Fill -> Hash -> Sign strip
advances. The step boxes are also buttons: click one to jump to (and
replay) that state; the first click cancels the auto-play so a presenter
can drive it manually. Gated behind prefers-reduced-motion.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/slides/EventAnatomySlide.vue

@@ -1,4 +1,5 @@
 <script setup lang="ts">
+import { onBeforeUnmount, onMounted, ref } from 'vue'
 import { PenLine, Hash, KeyRound, ArrowRight } from '@lucide/vue'
 import SlideShell from './SlideShell.vue'
 
@@ -29,6 +30,40 @@ const steps = [
   { icon: Hash, label: 'Hash them → id', sub: 'sha256 of the serialized event' },
   { icon: KeyRound, label: 'Sign id → sig', sub: 'Schnorr signature with your nsec' },
 ]
+
+// Staged reveal: typed fields first, then `id` is hashed in, then `sig` is signed in.
+// stage 0 = fields only · 1 = id computed · 2 = sig computed.
+const stage = ref(0)
+const timers: ReturnType<typeof setTimeout>[] = []
+
+function isRevealed(f: Field): boolean {
+  if (!f.derived) return true
+  if (f.key === 'id') return stage.value >= 1
+  return stage.value >= 2 // sig
+}
+
+function clearTimers() {
+  timers.forEach(clearTimeout)
+  timers.length = 0
+}
+
+// Click a step to jump to (and replay) that state; stops the auto-play so
+// manual control wins.
+function selectStage(i: number) {
+  clearTimers()
+  stage.value = i
+}
+
+onMounted(() => {
+  const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches
+  if (reduce) {
+    stage.value = 2
+    return
+  }
+  timers.push(setTimeout(() => (stage.value = 1), 900))
+  timers.push(setTimeout(() => (stage.value = 2), 1800))
+})
+onBeforeUnmount(clearTimers)
 </script>
 
 <template>
@@ -45,12 +80,20 @@ const steps = [
           >
             "{{ f.key }}"<span class="text-zinc-500">:</span>
           </span>
-          <span class="whitespace-nowrap" :class="valueClass[f.kind]"
-            >{{ f.value }}<span v-if="i < fields.length - 1" class="text-zinc-500">,</span></span
-          >
+          <span class="whitespace-nowrap" :class="valueClass[f.kind]">
+            <template v-if="isRevealed(f)">
+              <span :class="{ 'reveal-flash': f.derived }">{{ f.value }}</span
+              ><span v-if="i < fields.length - 1" class="text-zinc-500">,</span>
+            </template>
+            <span v-else class="italic text-zinc-600">{{
+              f.key === 'id' ? 'hashing…' : 'signing…'
+            }}</span>
+          </span>
           <span class="whitespace-nowrap text-sm text-zinc-600">
             <span class="text-zinc-500">// </span>{{ f.comment
-            }}<span v-if="f.derived" class="ml-1 rounded bg-violet-500/15 px-1 text-xs text-violet-300"
+            }}<span
+              v-if="f.derived && isRevealed(f)"
+              class="reveal-flash ml-1 rounded bg-violet-500/15 px-1 text-xs text-violet-300"
               >computed</span
             >
           </span>
@@ -63,19 +106,34 @@ const steps = [
     <!-- How it's built & signed -->
     <div class="mt-8 flex flex-col items-stretch gap-3 sm:flex-row sm:items-center sm:justify-center">
       <template v-for="(s, i) in steps" :key="s.label">
-        <div class="flex items-center gap-3 rounded-xl border border-zinc-700 bg-zinc-900/60 px-4 py-3">
-          <component :is="s.icon" class="h-6 w-6 flex-none text-violet-400" />
+        <button
+          type="button"
+          :aria-current="i === stage ? 'step' : undefined"
+          class="flex items-center gap-3 rounded-xl border px-4 py-3 text-left transition-colors duration-300 hover:border-violet-500/70 focus:outline-none focus-visible:ring-2 focus-visible:ring-violet-400"
+          :class="
+            i === stage
+              ? 'border-violet-500 bg-violet-950/30 ring-1 ring-violet-500/40'
+              : 'border-zinc-700 bg-zinc-900/60 hover:bg-zinc-900'
+          "
+          @click="selectStage(i)"
+        >
+          <component
+            :is="s.icon"
+            class="h-6 w-6 flex-none transition-colors duration-300"
+            :class="i === stage ? 'text-violet-300' : 'text-violet-400/60'"
+          />
           <div>
             <p class="font-semibold text-white">{{ s.label }}</p>
             <p class="text-xs text-zinc-400">{{ s.sub }}</p>
           </div>
-        </div>
+        </button>
         <ArrowRight
           v-if="i < steps.length - 1"
           class="mx-auto h-5 w-5 flex-none rotate-90 text-zinc-500 sm:rotate-0"
         />
       </template>
     </div>
+    <p class="mt-3 text-center text-xs text-zinc-600">Click a step to walk through each state.</p>
 
     <p class="mt-6 text-center text-sm text-zinc-500">
       Anyone recomputes the hash and checks <code class="text-zinc-300">sig</code> against your
@@ -83,3 +141,30 @@ const steps = [
     </p>
   </SlideShell>
 </template>
+
+<style scoped>
+.reveal-flash {
+  display: inline-block;
+  border-radius: 3px;
+  animation: reveal 0.6s ease-out;
+}
+@keyframes reveal {
+  0% {
+    opacity: 0;
+    filter: blur(5px);
+    box-shadow: 0 0 0 4px rgba(139, 92, 246, 0.35);
+    background: rgba(139, 92, 246, 0.35);
+  }
+  100% {
+    opacity: 1;
+    filter: blur(0);
+    box-shadow: 0 0 0 0 transparent;
+    background: transparent;
+  }
+}
+@media (prefers-reduced-motion: reduce) {
+  .reveal-flash {
+    animation: none;
+  }
+}
+</style>