An extensionless link is queued as a page, so the page worker navigated to
it in headless Chrome. When such a link served a binary, a zip or a CSV,
Chrome saved the file to the user's Downloads folder, a surprise side effect
of a clone (issue #32).
Deny Chrome-initiated downloads browser-wide, since kage fetches every asset
through its own downloader and never needs the browser to write a file. Then
watch the main document's response, and when it is not HTML, return a typed
ErrNotHTML so the page worker reroutes the URL to the asset downloader, where
the existing size and media policy decides whether to localise it or leave it
on the live web.
Verified against the two URLs from the issue, a zip and a CSV: both land
under the mirror's reserved tree and nothing is written to Downloads.
Duc-Tam Nguyen
bf850c6b93