Build-time /cv.pdf artifact

From LATER.md: "a wanted feature, not a maybe". Build-time `/cv.pdf` artifact (ChromicPDF or similar) rendered from the print stylesheet that already produces a clean one-pager. Browser print stays the baseline until the toolchain cost (headless Chrome in the build) is justified; if pursued, must stay optional so default builds keep zero native deps and byte-determinism.

Start with the LATER.md entry and the existing print stylesheet that produces the one-page CV. Compare the browser print baseline with a build-time /cv.pdf path, then assess whether the optional toolchain can preserve zero native dependencies in default builds and byte-determinism. Done means the artifact is optional and those default-build constraints remain intact.

Written by the indexing model from the issue text.