Preserve PPR gating for prerender route matchers
The matcher-model refactor separated fallback matcher metadata from concrete prerender outputs, but it unintentionally collected that metadata for non-PPR routes. Previously, routes with unresolved params were promoted to dynamic prerender entries only when route-level PPR was enabled.\n\nKeep the new representation behavior-preserving by retaining that PPR gate while extracting matcher directives. This prevents non-PPR outputs with parallel-route fallback params from being represented as both static outputs and dynamic matchers.
