Emits the runtime for search: "cherry", Cherry's built-in search
engine: search/index.json and the search/search.js island.
Unlike Stages.Post — which shells out to Pagefind — this stage is a
pure function of the parsed documents, so it runs anywhere cherry
itself runs and lands inside the deterministic build.
The island ships from here rather than from each theme's assets/,
so any theme, including one a site wrote itself, gets a working
search box by rendering the markup and pointing at these paths.
Runs after Machine and before Emit: the index is a runtime data
file, not part of the human site or the machine surface, so it stays
out of the sitemap, the feeds, and llms.txt.