Directory project artifact

This artifact is a directory at static/spa/example-directory/, served at /spa/example-directory/. Its stylesheet, its script and its data all ship beside the page, so every request it makes is same-origin.

An external same-origin script needs no hash at all: script-src 'self' already allows it. That is why a directory-shaped artifact is the easy case, and why the single-file shape needed the hash pipeline before it could be shipped.