The tracker-pattern source ranking collapsed HTTP into the PRE_EXISTING
tier, so a cookie first enumerated as pre-existing and later re-observed
only via a Set-Cookie response header stayed pre-existing. That left it
on the agent-skipped tier (isPreExistingSource), even though an HTTP
server-set cookie is real page evidence, not the extension-state
catch-all the skip was built to suppress.
Give HTTP its own rank between SCRIPT and EXTENSION
(SCRIPT > HTTP > EXTENSION > PRE_EXISTING) in both sourceRank and the
bestSource merge rollup, so an HTTP re-detection now promotes the
pattern and re-arms mapping, unblocking the identification agent.
Signed-off-by: Émile Ré <emile@probo.com>