v3: Model-vs-Market scoreboard — frozen forecasts, fair scoring, live page

- prediction_snapshots: model + de-vigged market frozen ≤15min pre-kickoff
  (or at first sight of a live match, flagged 'late' and excluded from totals).
- src/lib/model/scoring.ts: ONE shared RPS/Brier/log-loss implementation for
  the backtest and the live scoreboard.
- /api/scoreboard + /scoreboard page: per-match model-vs-bookmaker bars, RPS
  for both after FT, 'closer' badges, running head-to-head with honest rules
  printed (small-sample caveat included). Nav: 'vs Market'.
- Methodology page now shows the three-way split + ensemble bake-off variants.
- Verified end-to-end with a simulated match: snapshot froze model 80.7% and
  DraftKings 67.0% (de-vig correct), both scored at FT, late-flag honored.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/src/index.ts

@@ -9,6 +9,7 @@ import { TournamentState } from './tournament';
 import { startScheduler } from './ingest/scheduler';
 import { ModelEngine } from './model';
 import { buildPreview, buildTeamProfile } from './preview';
+import { buildScoreboard, snapshotCheck } from './scoreboard';
 import { db, healthAll, oddsFor, latestOddsAll } from './db/db';
 import { canonicalTeam } from '../../src/lib/teams';
 import type { MatchStatus, ServerMessage } from '../../src/lib/types';
@@ -59,6 +60,7 @@ export function buildServer() {
   app.get('/api/sources/health', async () => ({ sources: healthAll() }));
   // Bookmaker odds (benchmark for the Model-vs-Market scoreboard; not a model input)
   app.get('/api/odds', async () => ({ odds: latestOddsAll() }));
+  app.get('/api/scoreboard', async () => buildScoreboard(state));
   app.get('/api/odds/:num', async (req, reply) => {
     const num = Number((req.params as { num: string }).num);
     if (!Number.isFinite(num)) return reply.code(400).send({ error: 'bad num' });
@@ -93,6 +95,7 @@ export function buildServer() {
         'football-data',
       );
       if (!f) return reply.code(404).send({ error: 'no such fixture' });
+      snapshotCheck(state, model);
       broadcast();
       return { ok: true, fixture: f };
     });
@@ -125,7 +128,10 @@ export function buildServer() {
   });
 
   // ---- ingestion scheduler (ESPN primary; football-data / SofaScore fallback) ----
-  const stopIngest = startScheduler(state, () => broadcast());
+  const stopIngest = startScheduler(state, () => broadcast(), () => {
+    const taken = snapshotCheck(state, model);
+    if (taken) console.log(`[scoreboard] froze ${taken} pre-kickoff forecast(s)`);
+  });
   app.addHook('onClose', async () => stopIngest());
 
   // ---- static SPA (prod) with history fallback ----