Deserialize each route once when loading the manifest (#17415)

deserializeManifest deserialized every route twice: once for the
returned routes array, and again onto the input object, which nothing
reads afterwards. Both callers pass a fresh manifest they never read
back, and the returned routes are separate copies, so dropping the
second pass does not change behavior.

Co-authored-by: Matthew Phillips <matthewphillips@cloudflare.com>

Author: iseraph-dev

.changeset/dedupe-route-deserialization.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Deserializes each route once when loading the SSR manifest

packages/astro/src/core/app/manifest.ts

@@ -23,9 +23,6 @@ export function deserializeManifest(
 				...serializedRoute,
 				routeData: deserializeRouteData(serializedRoute.routeData),
 			});
-
-			const route = serializedRoute as unknown as RouteInfo;
-			route.routeData = deserializeRouteData(serializedRoute.routeData);
 		}
 	}
 	if (routesList) {