Read integrity, as-of context, and the shadow matchup resolve (A1-A7)

Seven orders of measurement-first repair. The served grade does not move.

A0/A1 — the unordered page walk returned the right COUNT and the wrong ROWS:
410-617 of 2,490 duplicated with an equal number never returned, while
rows.length matched the server exactly. safePaginate orders on a real unique
key, verifies the tuple at runtime, and THROWS on a query error instead of
treating it as end-of-data. Both hits PROVES are withdrawn: they were drawn
through that reader, and defense_by_direction's distinct-n was likely below
the gate floor all along.

A2/A2b — rolled across every reader: 11 FAIL -> 0. Composite keys pulled from
pg_index (the context tables are dated-composite and had no single unique
column). The unordered helper is deleted, not parked.

A3 — ledgerService and retentionService defaulted the SAME env var to
DIFFERENT versions, so no ledger row ever carried the marker eligibility
requires. One source now. model_snapshots settlement moved onto the cron:
15,484 -> 28,894 settled, repaired-champion 0 -> 7,556.

A4 — hitsFactorContext takes an as-of cutoff. Refusal over reconstruction: no
row at-or-before the date means the factor does not apply, never the nearest
row. Live path unchanged, proven 400/400 on real rows.

A5 — factor_inputs freezes what the factor READ, never the multiplier, so an
audit can recompute and check. It also recorded the finding: the three hits
factors have NEVER fired. prop.opponent and prop.opposing_pitcher are read by
the resolver and written by nothing.

A6/A7 — matchupKeys resolves those keys from the posted lineup plus the
schedule's probable pitchers, and fires the factors into a SHADOW freeze:
248 fires on 308 props, 245 of which would move the grade. The served
forecast is untouched. specs/a8-shadow-factor-gate.md pre-registers the test
that decides whether they ever go live.

Nothing is turned on. CALIBRATION_DEPLOYED stays []. Both verdicts stay
withdrawn. 4,772 tests / 371 suites green, web build exit 0, read-integrity
harness 34/34.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/services/gradeSlateService.js

@@ -101,8 +101,15 @@ async function gradeBestSide(grade, prop, sport, opts = {}) {
   // previously computed downstream of the grade it should inform.
   const factorContext = typeof opts.factorContext === 'function'
     ? opts.factorContext(prop, sport) : null;
+  // FIX A6 — the SHADOW pair. `factor_context` (above) is the LIVE context and
+  // is unchanged; these two let the engine compute what the factors WOULD do
+  // with the join keys, and freeze it. Neither reaches the served forecast.
+  const matchupKeys = typeof opts.matchupKeys === 'function'
+    ? opts.matchupKeys(prop, sport) : null;
   const base = {
     factor_context: factorContext,
+    factor_context_resolver: typeof opts.factorContext === 'function' ? opts.factorContext : null,
+    matchup_keys: matchupKeys,
     player: prop.player,
     stat_type: prop.stat_type,
     line: prop.line,