Fix workspace navigation regression on web (#772)

Centralize workspace navigation behind a small route-derived API so the workspace shell reads active selection from the current Expo Router route instead of a separately synchronized store.

Remove the stale layout-driven active-workspace write that regressed web after 02e5b564.

packages/app/src/hooks/use-workspace-navigation.ts

@@ -1,61 +1,16 @@
 import { useCallback } from "react";
-import { router } from "expo-router";
-import {
-  activateNavigationWorkspaceSelection,
-  getNavigationActiveWorkspaceSelection,
-} from "@/stores/navigation-active-workspace-store";
-import { buildHostWorkspaceRoute, parseHostWorkspaceRouteFromPathname } from "@/utils/host-routes";
+import { navigateToWorkspace } from "@/stores/navigation-active-workspace-store";
 
-interface NavigateToWorkspaceOptions {
-  currentPathname?: string | null;
-}
-
-function shouldUseRetainedWorkspaceSwitch(input: {
-  hasActiveWorkspace: boolean;
-  currentPathname?: string | null;
-}): boolean {
-  if (!input.hasActiveWorkspace) {
-    return false;
-  }
-
-  if (input.currentPathname == null) {
-    return false;
-  }
-
-  return parseHostWorkspaceRouteFromPathname(input.currentPathname) !== null;
-}
-
-/**
- * Open a workspace. Once the workspace shell is mounted, switching workspaces
- * is app-level state so native-stack does not rebuild every retained screen.
- */
-export function navigateToWorkspace(
-  serverId: string,
-  workspaceId: string,
-  options: NavigateToWorkspaceOptions = {},
-) {
-  const activeWorkspace = getNavigationActiveWorkspaceSelection();
-  if (
-    shouldUseRetainedWorkspaceSwitch({
-      hasActiveWorkspace: activeWorkspace !== null,
-      currentPathname: options.currentPathname,
-    })
-  ) {
-    activateNavigationWorkspaceSelection(
-      { serverId, workspaceId },
-      { updateBrowserHistory: true, historyMode: "push" },
-    );
-    return;
-  }
-
-  const href = buildHostWorkspaceRoute(serverId, workspaceId);
-  router.dismissTo(href);
-}
+export { navigateToWorkspace };
 
 export function useWorkspaceNavigation() {
   return {
     navigateToWorkspace: useCallback(
-      (serverId: string, workspaceId: string, options?: NavigateToWorkspaceOptions) => {
+      (
+        serverId: string,
+        workspaceId: string,
+        options?: Parameters<typeof navigateToWorkspace>[2],
+      ) => {
         navigateToWorkspace(serverId, workspaceId, options);
       },
       [],