Fix back swipe opening the drawer after a cold-start deep link (#11065)

Co-authored-by: Claude <noreply@anthropic.com>

src/lib/routes/helpers.ts

@@ -13,12 +13,20 @@ export function getRootNavigation<T extends {}>(
 
 export function getCurrentRoute(state?: State) {
   if (!state) {
-    return {name: 'Home'}
+    return {name: 'Home', params: undefined}
   }
 
+  /*
+   * Nested navigator states may still be partial ("stale") right after a cold
+   * start from a deep link, in which case `index` is not set yet. React
+   * Navigation focuses the last route when it rehydrates such a state, so
+   * mirror that here instead of stopping the descent early and misreporting
+   * the tab root as the current route (which e.g. re-enabled the drawer
+   * swipe gesture on top of a deep-linked screen).
+   */
   let node = state.routes[state.index || 0]
-  while (node.state?.routes && typeof node.state?.index === 'number') {
-    node = node.state?.routes[node.state?.index]
+  while (node.state?.routes) {
+    node = node.state.routes[node.state.index ?? node.state.routes.length - 1]
   }
   return node
 }
@@ -83,15 +91,24 @@ export function buildStateObject(
 ) {
   if (stack === 'Flat') {
     return {
+      index: 0,
       routes: [{name: route, params}],
     }
   }
+  /*
+   * Set `index` explicitly so consumers of this state (e.g. getCurrentRoute)
+   * can tell which route is focused before React Navigation has rehydrated
+   * the nested navigator state.
+   */
+  const routes = [...state, {name: route, params}]
   return {
+    index: 0,
     routes: [
       {
         name: stack,
         state: {
-          routes: [...state, {name: route, params}],
+          index: routes.length - 1,
+          routes,
         },
       },
     ],