fix(wix-deploy): expose Wix pages manifest for sitemaps

[omeb]

What

Serve /_wix/pages.json from the generated Wix BaaS handler. The endpoint converts Jay route instances into the page-manifest format consumed by Wix Site Structure.

Why

Wix-managed headless sitemap generation discovers frontend pages through this endpoint. Jay deployments currently return 404, so Site Structure sees zero pages and /sitemap.xml also returns 404.

Behavior

• Enumerates concrete built route instances as static Wix pages.
• Includes static routes without instances.
• Excludes noIndex, devOnly, and unbounded dynamic routes.
• Handles root, parameter, optional, required catch-all, and optional catch-all routes.
• Deduplicates and normalizes paths.

Validation

• 3 focused test cases pass, covering all route forms and exclusions above.
• TypeScript strict check passes for the manifest converter.
• Prettier and git diff --check pass.
• SSR package bundle builds with the new subpath export.
• The packed package contains dist/wix-pages-manifest.js, and the export resolves at runtime.
• Generated entry source passes an esbuild syntax/bundle check.
• Live pre-fix reproduction: https://www.jay-framework.dev/_wix/pages.json returns the exact 404 Not Found response from the old handler.