v3 Phase B core: Team-DC + backtested ensemble, squad values

- src/lib/model/teamDc.ts: per-team attack/defence Dixon-Coles via weighted MLE
  (Maher iterations), exponential time-decay, shrinkage for thin histories,
  learned home multiplier; log-pool of score matrices. 7 vitest cases.
- buildBacktest.ts rewritten as a strict three-way-split bake-off: params
  pre-2018, tune (xi, k, w) on 2018-2022 validation, final scores on untouched
  2022-2026 test (4,448 matches). Result: ensemble RPS 0.1721 beats Elo-DC
  0.1726 and Team-DC 0.1801; ECE stays 0.01. Tuned: xi=0.5 k=5 w=0.75.
- Runtime now IS the backtested model: ratings.json carries teamDc+ensembleW;
  matchMatrix() pools both members for predictions, Monte Carlo and advance
  probs; ModelEngine re-rating preserves ensemble params; lambdas reported as
  matrix expectations (drives in-play).
- scripts/buildSquadValues.ts: Transfermarkt FIWC participants page -> all 48
  squad market values (France 1.52bn ... Qatar 20m). Display/availability layer
  only — June-2026 values are NOT in the backtested model (would leak).

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

scripts/buildRatings.ts

@@ -9,6 +9,14 @@ import { dirname, join } from 'node:path';
 import { canonicalTeam, ALL_TEAMS } from '../src/lib/teams';
 import { HOME_ADV_ELO, importanceWeight, eloDelta, expectedHome } from '../src/lib/model/elo';
 import { poissonPmf } from '../src/lib/model/poisson';
+import { fitTeamDc, type DcMatch } from '../src/lib/model/teamDc';
+
+// Ensemble hyper-params — tuned on the 2018–2022 validation window and verified
+// out-of-sample on 2022–2026 by scripts/buildBacktest.ts. Keep in sync with it.
+const TEAMDC_XI = 0.5;
+const TEAMDC_SHRINK_K = 5;
+const ENSEMBLE_W = 0.75; // log-pool weight on the Elo-DC member
+const FIT_WINDOW_YEARS = 15;
 
 const ROOT = join(dirname(fileURLToPath(import.meta.url)), '..');
 const CSV = join(ROOT, 'data', 'raw', 'international-results.csv');
@@ -119,6 +127,27 @@ function main(): void {
   // Ensure every WC team has a rating (default for any never seen).
   for (const t of ALL_TEAMS) if (!(t in ratings)) ratings[t] = START_ELO;
 
+  // ---- Team-DC ensemble member: fit on the recent window through today ----
+  const nowT = new Date(lastDate).getTime();
+  const windowMs = FIT_WINDOW_YEARS * 365 * 24 * 60 * 60 * 1000;
+  const dcTrain: DcMatch[] = [];
+  for (const r of rows) {
+    const t = new Date(r.date).getTime();
+    if (nowT - t > windowMs) continue;
+    dcTrain.push({
+      daysAgo: (nowT - t) / (24 * 60 * 60 * 1000),
+      home: canonicalTeam(r.home), away: canonicalTeam(r.away),
+      homeGoals: r.hs, awayGoals: r.as, neutral: r.neutral,
+    });
+  }
+  const teamDc = fitTeamDc(dcTrain, TEAMDC_XI, TEAMDC_SHRINK_K);
+  // Trim to relevant nations: WC qualifiers + any team rated (keeps file small).
+  const keep = new Set<string>([...ALL_TEAMS, ...Object.keys(ratings)]);
+  teamDc.attack = Object.fromEntries(Object.entries(teamDc.attack).filter(([t]) => keep.has(t)).map(([t, v]) => [t, Math.round(v * 1e4) / 1e4]));
+  teamDc.defence = Object.fromEntries(Object.entries(teamDc.defence).filter(([t]) => keep.has(t)).map(([t, v]) => [t, Math.round(v * 1e4) / 1e4]));
+  teamDc.mu = Math.round(teamDc.mu * 1e4) / 1e4;
+  teamDc.homeMult = Math.round(teamDc.homeMult * 1e4) / 1e4;
+
   const out = {
     generatedAt: new Date().toISOString(),
     asOf: lastDate,
@@ -131,6 +160,8 @@ function main(): void {
       rho,
       homeAdvElo: HOME_ADV_ELO,
     },
+    teamDc,
+    ensembleW: ENSEMBLE_W,
     ratings,
   };