feat(champ): stream champion-spawn state to the sidecar board

Champion spawns have no ServUO EventSink, so add a fourth polled stream
(BridgeChamps) modeled on BridgeSweeps: enumerate every spawn each tick,
fold to a small record, and emit champ.update only on change. No core
patch — every field used is public.

Covers all three families via a `category` field:
  - champion: ChampionSpawn (type/level/kills/boss/cooldown ETA)
  - mini:     MiniChamp (type/level; auto-restarts, no kill counter)
  - sea:      BaseSeaChampion (a High Seas world-boss mobile, alive only
              while summoned; removed via champ.remove when slain)

Status folds to active/cooldown/dormant. A (re)connection clears the diff
cache so the next sweep re-emits the full board, rebuilding a sidecar that
restarted on its own. Transient entries leave via champ.remove.

Sidecar: a `champs` current-state table (one row per serial) fed by
champ.update (upsert) and champ.remove (delete), exposed at GET /champs as
the live board. New ChampSweepSeconds config (default 10s), wired into
[bridge reload/sweepnow/status. Documented in docs/INTEGRATION.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0114TpmrNW4wNXsHq5CR72jQ

sidecar/src/main.rs

@@ -105,6 +105,35 @@ async fn main() -> anyhow::Result<()> {
                 if let Err(e) = event_store.insert_event(t, &ev.kind, &text).await {
                     tracing::warn!(error = %e, "failed to persist event");
                 }
+
+                // The champ board is a live projection: champ.update folds in the latest state (one
+                // row per spawn), champ.remove drops a spawn that despawned or was slain.
+                match ev.kind.as_str() {
+                    "champ.update" => {
+                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
+                            if let Err(e) = event_store
+                                .upsert_champ(
+                                    serial,
+                                    ev.value.get("status").and_then(|s| s.as_str()),
+                                    ev.value.get("name").and_then(|n| n.as_str()),
+                                    &text,
+                                    t,
+                                )
+                                .await
+                            {
+                                tracing::warn!(error = %e, "failed to upsert champ board");
+                            }
+                        }
+                    }
+                    "champ.remove" => {
+                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
+                            if let Err(e) = event_store.delete_champ(serial).await {
+                                tracing::warn!(error = %e, "failed to remove champ board row");
+                            }
+                        }
+                    }
+                    _ => {}
+                }
             }
 
             let _ = feed_tx.send(ev.value.to_string());