Model Train arc 1 (engine): de-vig + EV + takeable/value gates + hero v2 + triplet

Steps 1-6 — make "real opportunities at takeable prices" the engine, not a filter.

1. DE-VIG (src/utils/devig.js): two-way multiplicative de-vig strips the vig and
   returns fair prob + fair price per side + the overround. One side missing →
   fair UNAVAILABLE (null), never faked. Method noted in code + the `devig_method`
   field.
2. EV (devig.evPct): ev_pct = model prob × decimal − 1 at the graded side's
   ACTUAL price. This is the ranking signal now, replacing raw |model−consensus|.
3. TAKEABLE gate (src/config/valueEngine.js, TAKEABLE_ODDS_CEILING −160 .. +200,
   env-tunable): promoted surfaces only (hero/featured/alerts). The full board
   still shows everything; Parlay Lab exempt; JUICE_ODDS_FLOOR (−400) stays the
   absolute backstop underneath. Strict null-guard (Number(null)===0 would have
   made a missing price "takeable").
4. VALUE flag: passes BOTH gates (takeable AND ev_pct ≥ VALUE_EV_THRESHOLD).
   Grade = read quality; value = the price pays you. Shipped in payloads.
5. HERO v2 (heroPropService): highest ev_pct among takeable A/B reads — a huge
   gap on a −900 line is trivia, not an opportunity.
6. VALUE TRIPLET: book_odds · fair_odds · model_odds on every read (snapshot,
   hero, scan — they all spread the grade). Handoff documents the fields; the
   rendering is Session-2 Design's job.

All wired in analyzeViaEngine1's existing p_win/kelly block (real quantile
probability × real book odds, or nothing). 33 new tests; suite 276/3306 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/config/valueEngine.js

@@ -0,0 +1,49 @@
+'use strict';
+
+/**
+ * Value engine config (Model Train, steps 3-4).
+ *
+ * Product doctrine (Kev): VYNDR PROMOTES bets people actually take — roughly the
+ * -160 to +200 band — that ALSO carry a genuine vig-free edge. Not
+ * plus-money-only, not heavy chalk.
+ *
+ * The TAKEABLE gate applies to PROMOTED surfaces only (daily hero, featured /
+ * top-of-board, future alerts). The full board still shows every graded read.
+ * Parlay Lab is EXEMPT (juiced legs combine into takeable payouts).
+ * JUICE_ODDS_FLOOR (-400, in rareEventMarkets) stays the absolute refusal
+ * backstop UNDERNEATH this — those reads are never graded at all.
+ *
+ * All thresholds are env-tunable.
+ */
+
+// The promotable price band. Ceiling = most-juiced favorite we'll promote;
+// max = longest dog we'll promote.
+const TAKEABLE_ODDS_CEILING = Number(process.env.TAKEABLE_ODDS_CEILING || -160);
+const TAKEABLE_ODDS_MAX = Number(process.env.TAKEABLE_ODDS_MAX || 200);
+
+// A read is VALUE only when its EV clears this (a real edge, not rounding).
+const VALUE_EV_THRESHOLD = Number(process.env.VALUE_EV_THRESHOLD || 2);
+
+/** Is an American price inside the takeable band (default -160..+200)?
+ *  Strict on input — null/''/undefined are NOT takeable (Number(null) === 0
+ *  would otherwise land a missing price inside the band). */
+function isTakeable(american) {
+  if (american == null || american === '') return false;
+  const a = Number(american);
+  if (!Number.isFinite(a)) return false;
+  return a >= TAKEABLE_ODDS_CEILING && a <= TAKEABLE_ODDS_MAX;
+}
+
+/** A read carries VALUE when it's takeable AND its EV clears the threshold —
+ *  "the price pays you to take it", distinct from grade ("read quality"). */
+function isValue(american, evPct) {
+  return isTakeable(american) && Number.isFinite(evPct) && evPct >= VALUE_EV_THRESHOLD;
+}
+
+module.exports = {
+  TAKEABLE_ODDS_CEILING,
+  TAKEABLE_ODDS_MAX,
+  VALUE_EV_THRESHOLD,
+  isTakeable,
+  isValue,
+};