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/web.rs

@@ -70,6 +70,7 @@ pub async fn serve(addr: &str, state: AppState) -> anyhow::Result<()> {
         // History, read from SQLite rather than the shard.
         .route("/history", get(history))
         .route("/economy", get(economy))
+        .route("/champs", get(champs))
         .route_layer(middleware::from_fn_with_state(state.clone(), gate));
 
     let app = Router::new()
@@ -552,6 +553,19 @@ async fn economy(State(st): State<AppState>, Query(q): Query<HistoryQuery>) -> i
     }
 }
 
+/// The champion-spawn board: every spawn's latest state (status/level/kills/boss/location and, when
+/// relevant, the cooldown ETA). Served from the local board table, so it answers without touching
+/// the shard and survives a shard outage with the last-known snapshot.
+async fn champs(State(st): State<AppState>) -> impl IntoResponse {
+    match st.store.champs_all().await {
+        Ok(spawns) => (StatusCode::OK, Json(json!({"spawns": spawns}))),
+        Err(e) => (
+            StatusCode::INTERNAL_SERVER_ERROR,
+            Json(json!({"error": e.to_string()})),
+        ),
+    }
+}
+
 // ---- websocket ----
 
 async fn ws_upgrade(ws: WebSocketUpgrade, State(state): State<AppState>) -> impl IntoResponse {