Sigurd doesn't trigger on a saga's first lore counter, when it enters the battlefield


I have [[Sigurd, Jarl of Ravensthorpe]] on the battlefield, and [[Ballad of the Black Flag]] enters. A lore counter is put on that saga as it enters, causing the saga itself to trigger (and [[Historian's Boon]]) but not Sigurd himself.

No files or tests are named. Start by locating the implementations of Sigurd, Ballad of the Black Flag, and saga enter-the-battlefield trigger handling, then trace how the first lore counter is processed. Done means Sigurd triggers when the saga enters with its first lore counter, with a regression test covering this interaction.

Written by the indexing model from the issue text.