Fix composer horizontal swipe triggering browser back/forward

Two-finger horizontal trackpad swipes over the composer were escaping to
the page's history-nav gesture, especially obvious when a quote post was
attached. Mirror the carousel fix: `overscroll-behavior-x: contain` on
the composer's ScrollView for Chrome/Firefox, plus a wheel listener that
preventDefaults horizontal-dominant wheels for Safari (which ignores
overscroll-behavior).

src/view/com/composer/Composer.tsx

@@ -134,7 +134,14 @@ import * as Prompt from '#/components/Prompt'
 import * as Toast from '#/components/Toast'
 import {Text} from '#/components/Typography'
 import {useAnalytics} from '#/analytics'
-import {IS_ANDROID, IS_IOS, IS_LIQUID_GLASS, IS_NATIVE, IS_WEB} from '#/env'
+import {
+  IS_ANDROID,
+  IS_IOS,
+  IS_LIQUID_GLASS,
+  IS_NATIVE,
+  IS_WEB,
+  IS_WEB_SAFARI,
+} from '#/env'
 import {type Gif} from '#/features/gifPicker/types'
 import {BottomSheetPortalProvider} from '../../../../modules/bottom-sheet'
 import {
@@ -1219,6 +1226,24 @@ export const ComposePost = ({
     }
   }, [composerState])
 
+  useEffect(() => {
+    // Safari ignores `overscroll-behavior`, so horizontal trackpad swipes over
+    // the composer (e.g. on a quote post) can still trigger the browser's
+    // back/forward navigation gesture. Suppress predominantly-horizontal wheel
+    // events so the history-nav gesture never fires. Chrome and Firefox are
+    // covered by the `overscrollBehaviorX: 'contain'` style on the ScrollView.
+    if (!IS_WEB_SAFARI) return
+    const el =
+      scrollViewRef.current?.getScrollableNode() as unknown as HTMLElement | null
+    if (!el) return
+    const onWheel = (e: WheelEvent) => {
+      if (Math.abs(e.deltaX) <= Math.abs(e.deltaY)) return
+      e.preventDefault()
+    }
+    el.addEventListener('wheel', onWheel, {passive: false})
+    return () => el.removeEventListener('wheel', onWheel)
+  }, [scrollViewRef])
+
   const isLastThreadedPost = thread.posts.length > 1 && nextPost === undefined
   const {
     scrollHandler,
@@ -1324,6 +1349,11 @@ export const ComposePost = ({
               web({
                 scrollbarGutter: 'stable',
                 scrollbarColor: `${t.palette.contrast_200} transparent`,
+                // Prevent horizontal trackpad swipes from triggering the
+                // browser's back/forward overscroll-navigation gesture.
+                // Handles Chrome and Firefox; Safari is handled separately
+                // via a wheel listener since it ignores overscroll-behavior.
+                overscrollBehaviorX: 'contain',
               }),
             ]}
             keyboardShouldPersistTaps="always"