tests: migrate Date.now patching to the pinned-clock parameter

The now parameter (and partialGraph.now) replaced the need for global
Date.now patching in tests. The ttl-expiry parity campaign's module-scope
patch and the relational-comparator Time-Based Decay tests' before/after
patches now pass the clock explicitly through check options — no global
mutation, no restore-order fragility, and the pinned-clock cache bypass
keeps every evaluation honest. No stale references to the removed
compiled evaluator or useCompiled option remain in the test suite.

tests/rigor/ttl-expiry-parity.test.js

@@ -23,9 +23,7 @@ const TTL = 5000;
 const DOCS = 2;
 const docKey = (i) => `doc:${i}`;
 
-const realNow = Date.now;
 let engineNow = 1_000_000_000_000;
-Date.now = () => engineNow;
 
 function makeWrapper(disableCaching) {
   const arbiter = new Arbiter(disableCaching ? { disableCaching: true } : {});
@@ -69,7 +67,7 @@ function makeWrapper(disableCaching) {
       return { ok: true, now: engineNow };
     },
     check(doc) {
-      const result = arbiter.check('user:alice', 'premium', docKey(doc));
+      const result = arbiter.check('user:alice', 'premium', docKey(doc), { now: engineNow });
       const b = balance.get(doc);
       const p = price.get(doc);
       const bFresh = b !== undefined && engineNow - b.ts <= TTL;