v10.4.2

The engine moved twice in a day and the agent lane has to move with it.
extension-develop 4.0.30 carries the MAIN-world public path fix: a
content script running in the page's own world now resolves extension
assets through the isolated-world bridge base instead of falling back to
the host page, where it 404'd.

• extension-create, extension-develop and extension-install move
  from 4.0.29 to 4.0.30. The nightly engine-pin job added in 10.4.1 is
  what would have caught this drift; the bump is the first it prompted.