Book Comparison Phase 1-3(backend): fenced per-book store + honest gated crown

Per-book prices existed only transiently (odds cache, ~1h, raw names, grade-path
input); every grade-path persistence point collapses to one book. The
/api/books feature was built+mounted but non-functional (fed FLAT rows to a
GROUPED comparator -> always empty).

Phase 1: bookPriceStore captures per-book prices from `props` BEFORE dedupeProps,
keyed nameKey|stat, into bookprices:{sport} (SNAP_TTL) in snapshotService. Fenced:
reads props, writes its own key, read by nothing on the grade path. Grade proven
byte-identical (test + no-grade-path-reference grep test).

Phase 2: scripts/measure-book-spread.js reports same-line best-vs-worst spread
(cents + implied-prob pts), per sport, never pooled. Pre-registered crown
threshold: median >=8c OR >=2pp. Runs post-deploy on real data.

Phase 3 (backend): compareProp is honest-absent (single-book/flat -> no crown)
and the crown is gated (BOOK_CROWN_ENABLED, default OFF until Phase 2 clears).
/api/books repointed to the snapshot-locked store (fallback odds cache),
nameKey-matched; `source` field is the deploy fingerprint.

HELD unchanged: dedupeProps, snapshot dedup, selector, grade, champion,
challengers, ranking, edge_pct/ev_pct. UI routing of BookComparison + crown
treatment deferred to post-measurement (gated on Phase 2). Full suite 3834 green,
web build exit 0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VsztNChZ7vEvSR61AuMhD1

src/services/snapshotService.js

@@ -284,6 +284,10 @@ async function runSnapshot(sport, opts = {}) {
     // suite that doesn't know about this dep can never make a live ESPN call.
     // Session 64 — model-snapshot retention. Injectable; null disables it.
     retention: opts.retention !== undefined ? opts.retention : require('./retentionService'),
+    // Book Comparison order (Phase 1) — DISPLAY-ONLY per-book price capture.
+    // Fenced: written to its own `bookprices:{sport}` key, read by nothing on
+    // the grade path. Injectable; a failure never touches grading.
+    captureBookPrices: opts.captureBookPrices || require('./bookPriceStore').captureBookPrices,
     refreshTeamStats: opts.refreshTeamStats
       || (process.env.NODE_ENV === 'test'
         ? async () => null
@@ -335,6 +339,21 @@ async function runSnapshot(sport, opts = {}) {
     console.warn(`[snapshot] game binding failed for ${sp} (rows without a real game time will be skipped):`, e.message);
   }
 
+  // Book Comparison order (Phase 1) — CAPTURE PER-BOOK PRICES BEFORE DEDUP.
+  // `props` still carries one row per book here (dedupeProps runs downstream
+  // inside gradeAndCacheSlate). The capture only READS props and writes its own
+  // `bookprices:{sport}` key at SNAP_TTL — long enough to outlive the cron gap
+  // (the 1h odds cache would blank between runs). Best-effort and structurally
+  // fenced: nothing on the grade path reads this key, and the graded slate is
+  // byte-identical whether or not this runs (bookPriceStore.test.js locks it).
+  try {
+    const bookStore = deps.captureBookPrices(props, { now: deps.now });
+    await deps.cacheSet(`bookprices:${sp}`, bookStore, SNAP_TTL);
+    console.log(`[snapshot] book prices ${sp}: ${bookStore.count} props with book rows captured`);
+  } catch (e) {
+    console.warn(`[snapshot] book-price capture failed for ${sp} (display-only, grading continues):`, e.message);
+  }
+
   // Session 63 — REFRESH TEAM STATS BEFORE GRADING.
   // `refreshTeamStats` is the ONLY writer of `team_stats:{sport}:{abbr}`, which
   // is the ONLY source of `opp_rank_stat` — and it had zero production callers,