S1 (a1): feature-promise audit — no claim survives unverified

PROMISE-AUDIT.md: every /pricing claim → verified/built/reworded.
BUILT (was vapor): alt line ladder + edge ranking (same-features regrade
at shifted lines, Desk-gated at the API), quarter-Kelly (engine quantile
P(win) x real captured odds — either missing → no sizing), free-tier
kill-condition locked previews. FIXED (was false): analyst 15/day cap vs
the Founder 'Unlimited reads' promise → analyst unlimited; every '40+
factors' claim (real count: 22 named features) reworded truthfully in 7
files. VERIFIED: cascade alerts (real, wired), phi correlation,
leg history, cross-book comparison, WC soccer, real-time feed.
Locked by tests/unit/promiseAudit.test.js. Jest now ignores
.claude/worktrees (parallel agents' suites no longer leak into runs).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/utils/kelly.js

@@ -0,0 +1,41 @@
+'use strict';
+
+/**
+ * Quarter-Kelly sizing (Session 62 / A1-S1 — the pricing page promised it;
+ * now it exists). Pure math, no I/O.
+ *
+ * DATA SEMANTICS: Kelly needs a REAL win probability and REAL book odds.
+ * p comes from the engine's quantile probability estimator (game-log based);
+ * odds come from the captured book row. Either missing → null — a sizing
+ * recommendation is never fabricated from confidence scores or defaults.
+ */
+
+function americanToDecimal(american) {
+  const a = Number(american);
+  if (!Number.isFinite(a) || a === 0) return null;
+  return a > 0 ? 1 + a / 100 : 1 + 100 / Math.abs(a);
+}
+
+/**
+ * quarterKelly(p, americanOdds) →
+ *   { full, quarter, pct } — fractions of bankroll (pct = quarter × 100,
+ *   rounded to 0.1) — or null when p/odds are unusable or the edge is
+ *   non-positive (Kelly says: no bet).
+ */
+function quarterKelly(p, americanOdds) {
+  const prob = Number(p);
+  if (!Number.isFinite(prob) || prob <= 0 || prob >= 1) return null;
+  const dec = americanToDecimal(americanOdds);
+  if (dec == null || dec <= 1) return null;
+  const b = dec - 1;
+  const full = (b * prob - (1 - prob)) / b;
+  if (!Number.isFinite(full) || full <= 0) return null;
+  const quarter = full / 4;
+  return {
+    full: Math.round(full * 1000) / 1000,
+    quarter: Math.round(quarter * 1000) / 1000,
+    pct: Math.round(quarter * 1000) / 10, // % of bankroll at quarter-Kelly
+  };
+}
+
+module.exports = { quarterKelly, americanToDecimal };