Rank HTTP cookie source above pre-existing

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>

pkg/cookiebanner/pattern_analysis_worker_test.go

@@ -1159,15 +1159,45 @@ func TestShouldPromoteSource(t *testing.T) {
 			want:      false,
 		},
 		{
-			name:      "HTTP collapses to PRE_EXISTING rank: does not promote SCRIPT",
+			name:      "HTTP does not promote to SCRIPT (HTTP ranks below SCRIPT)",
 			existing:  &script,
 			candidate: &http,
 			want:      false,
 		},
 		{
-			name:      "HTTP collapses to PRE_EXISTING rank: equal to nil existing",
+			name:      "nil existing promotes to HTTP",
 			existing:  nil,
 			candidate: &http,
+			want:      true,
+		},
+		{
+			name:      "PRE_EXISTING promotes to HTTP",
+			existing:  &preExisting,
+			candidate: &http,
+			want:      true,
+		},
+		{
+			name:      "EXTENSION promotes to HTTP (real server cookie outranks extension state)",
+			existing:  &extension,
+			candidate: &http,
+			want:      true,
+		},
+		{
+			name:      "HTTP promotes to SCRIPT",
+			existing:  &http,
+			candidate: &script,
+			want:      true,
+		},
+		{
+			name:      "HTTP does not promote to EXTENSION",
+			existing:  &http,
+			candidate: &extension,
+			want:      false,
+		},
+		{
+			name:      "HTTP does not promote to PRE_EXISTING",
+			existing:  &http,
+			candidate: &preExisting,
 			want:      false,
 		},
 	}