The vendored markit engine kept `mupdf` external, but a single-file
`bun --compile` binary has no node_modules to resolve it from, so the
standalone binary aborted at startup with `Cannot find package 'mupdf'`
— the otherwise-lazy import is resolved eagerly at boot. Bundle mupdf and
embed its WASM blob (scripts/embed-mupdf-wasm.ts, reset after the build);
npm and source installs still load mupdf from node_modules.
Import mupdf lazily inside the PDF converter so the bundled markit chunk's
init stays synchronous: mupdf's top-level await otherwise made the chunk
init async and bun's compiled bundler failed to await it through the
barrel, exposing the converters before their module-level const tables
initialized (undefined EXTENSIONS). Also keeps the ~10MB wasm off non-PDF
document conversions.
can1357