Fix deep link URL re-processing on account switch and back gesture reliability

Two fixes for initialUrl/deep link handling:

1. Prevent initial URL from being re-processed on account switch. The
   key={currentAccount?.did} in App.native.tsx remounts NavigationContainer,
   which re-calls getInitialURL() and navigates to the deep link again.
   Fixed by tracking consumption in a module-level flag and providing a
   custom getInitialURL that returns null after first call.

2. Fix back swipe gesture not working reliably from deep links. Two changes:
   - Changed isStateAtTabRoot to return false when state is undefined
     (during init), preventing the Drawer gesture from activating during
     the async window before the initial URL resolves.
   - Added custom subscribe handler that navigates (pushes) on native
     instead of letting React Navigation reset the entire state, ensuring
     proper native back gesture setup.

https://claude.ai/code/session_01NCogJsPSFXu8YJG8dWwEbC

src/Navigation.tsx

@@ -18,6 +18,7 @@ import {
 } from '@react-navigation/native'
 
 import {timeout} from '#/lib/async/timeout'
+import {parseLinkingUrl} from '#/lib/parseLinkingUrl'
 import {useAccountSwitcher} from '#/lib/hooks/useAccountSwitcher'
 import {useColorSchemeStyle} from '#/lib/hooks/useColorSchemeStyle'
 import {useNonReactiveCallback} from '#/lib/hooks/useNonReactiveCallback'
@@ -833,11 +834,60 @@ const FlatNavigator = ({
  * to the navigation context.
  */
 
+// Prevents re-processing the initial deep link URL on remount
+// (e.g. when account switch changes the key in App.native.tsx)
+let initialUrlConsumed = false
+
 const LINKING = {
   // TODO figure out what we are going to use
   // note: `bluesky://` is what is used in app.config.js
   prefixes: ['bsky://', 'bluesky://', 'https://bsky.app'],
 
+  async getInitialURL(): Promise<string | null> {
+    if (initialUrlConsumed) {
+      return null
+    }
+    initialUrlConsumed = true
+    return Linking.getInitialURL()
+  },
+
+  subscribe(listener: (url: string) => void) {
+    const sub = Linking.addEventListener('url', ({url}: {url: string}) => {
+      if (IS_NATIVE && navigationRef.isReady()) {
+        const urlp = parseLinkingUrl(url)
+        const path = urlp.pathname
+
+        // Intent URLs are handled by useIntentHandler
+        if (path.includes('intent/')) {
+          return
+        }
+
+        const [name, params] = router.matchPath(path)
+
+        // For tab roots, switch to the tab
+        if (name === 'Search') {
+          resetToTab('SearchTab')
+        } else if (name === 'Notifications') {
+          resetToTab('NotificationsTab')
+        } else if (name === 'Home') {
+          resetToTab('HomeTab')
+        } else if (name === 'Messages') {
+          resetToTab('MessagesTab')
+        } else {
+          // Navigate (push) instead of resetting state, so that the
+          // native back gesture is properly set up
+          // @ts-ignore nested navigators aren't typed -sfn
+          navigate('HomeTab', {screen: name, params})
+        }
+        return
+      }
+
+      // Web or navigation not ready: use default React Navigation behavior
+      listener(url)
+    })
+    return () => sub.remove()
+  },
+
   getPathFromState(state: State) {
     // find the current node in the navigation tree
     let node = state.routes[state.index || 0]

src/lib/routes/helpers.ts

@@ -25,11 +25,11 @@ export function getCurrentRoute(state?: State) {
 
 export function isStateAtTabRoot(state: State | undefined) {
   if (!state) {
-    // NOTE
-    // if state is not defined it's because init is occurring
-    // and therefore we can safely assume we're at root
-    // -prf
-    return true
+    // During initialization (before navigation state is set), default to
+    // not-at-root. This prevents the drawer gesture from activating during
+    // the async window before the initial URL is resolved, which would
+    // compete with the native stack's back gesture on deep link opens.
+    return false
   }
   const currentRoute = getCurrentRoute(state)
   return (