/**
 * Whether a file matched by the FileSystemRouter is actually a page.
 *
 * `Bun.FileSystemRouter` routes every file under `src/pages`, including
 * ones the bundler never builds: `.server.ts` companions, the `__root`
 * layout, tests, and paths excluded by `pages_exclude_patterns` (or inside
 * an excluded directory). Requests for those must 404 rather than wait for
 * a bundle that will never exist. Mirrors the rules in `grabAllPages`.
 */
export default function isRoutablePage(file_path: string): boolean;