milestone 21: abp list exceptions and a regex rule kind

src/web/handlers/lookup.zig

@@ -38,6 +38,8 @@ pub const Body = struct {
     reason: []const u8,
     /// The rule or list entry that decided it; "" when nothing matched.
     matched: []const u8,
+    /// The list that decided it, which for `blocklist_exception` is the list
+    /// whose `@@` rule lifted the block rather than one that made it.
     source_url: ?[]const u8,
     safe_search_rewrite: ?[]const u8,
 };
@@ -50,7 +52,8 @@ pub const Result = struct {
     blocked: bool,
     reason: matcher.Reason,
     matched: []const u8,
-    /// `blocklist_sources` row id of the list that matched.
+    /// `blocklist_sources` row id of the list that matched, whether it blocked
+    /// the name or lifted it through an `@@` exception.
     source_id: ?i64,
     safe_search_rewrite: ?[]const u8,
 };