🐛 fix: ignore taps that end a scroll on mobile

Some mobile browsers fire a click when a scroll gesture ends over a poster,
which opened it by accident. Swallow clicks from touches that moved or while
a scroll is still settling, so only real taps reach the app.

src/main.tsx

@@ -2,6 +2,9 @@ import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
 import './index.css'
 import App from './App'
+import { installTapGuard } from './tapGuard'
+
+installTapGuard()
 
 createRoot(document.getElementById('root')!).render(
   <StrictMode>

src/tapGuard.ts

@@ -0,0 +1,51 @@
+// Some mobile browsers (notably iOS, and installed web apps) fire a click when
+// a scroll gesture ends on top of a poster, which opens it by accident. This
+// swallows clicks that come from a touch that moved or from a scroll that was
+// still settling, so only real taps reach the app.
+
+const TAP_SLOP_PX = 10
+const SCROLL_SETTLE_MS = 120
+const TOUCH_CLICK_WINDOW_MS = 800
+
+export function installTapGuard() {
+  let startX = 0
+  let startY = 0
+  let moved = false
+  let lastTouchEndAt = 0
+  let lastScrollAt = 0
+
+  window.addEventListener('touchstart', (event) => {
+    const touch = event.touches[0]
+    startX = touch?.clientX ?? 0
+    startY = touch?.clientY ?? 0
+    moved = false
+  }, { capture: true, passive: true })
+
+  window.addEventListener('touchmove', (event) => {
+    const touch = event.touches[0]
+    if (touch && Math.hypot(touch.clientX - startX, touch.clientY - startY) > TAP_SLOP_PX) {
+      moved = true
+    }
+  }, { capture: true, passive: true })
+
+  window.addEventListener('touchend', () => {
+    lastTouchEndAt = Date.now()
+  }, { capture: true, passive: true })
+
+  // Scroll events don't bubble, so listen in the capture phase to see every
+  // scroll container (page, carousels, episode lists).
+  document.addEventListener('scroll', () => {
+    lastScrollAt = Date.now()
+  }, { capture: true, passive: true })
+
+  window.addEventListener('click', (event) => {
+    const now = Date.now()
+    if (now - lastTouchEndAt > TOUCH_CLICK_WINDOW_MS) {
+      return
+    }
+    if (moved || now - lastScrollAt < SCROLL_SETTLE_MS) {
+      event.preventDefault()
+      event.stopPropagation()
+    }
+  }, { capture: true })
+}