Storylines: the same site told several ways, one per visitor, counted

Any text a person reads may be a list, one entry per storyline, every
list the same length. A visitor is given one storyline for the whole
site and reads it on every page and in every mail about their case.
Records and events carry the storyline; GET /report gives counts per
bucket, storyline and state, and nothing else.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GT37Z1Xtfd9pUuQtMTg6Yt

src/announce.rs

@@ -84,6 +84,7 @@ pub async fn sweep(state: &AppState) -> anyhow::Result<()> {
                     EVENT_ALTERNATIVE,
                     &responses,
                     now_ms,
+                    0,
                 )
                 .await?;
                 tracing::info!(question = %q.id, "event record created");
@@ -137,6 +138,7 @@ pub async fn sweep(state: &AppState) -> anyhow::Result<()> {
                     alternative: SUMMARY_DUE_LABEL.to_string(),
                     responses: payload,
                     timestamp_ms: now_ms,
+                    storyline: 0,
                 },
             )
             .await?;