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;

tests/rules/relational-comparator.test.js

@@ -294,8 +294,6 @@ describe('RelationalComparatorRule Tests', () => {
   describe('Time-Based Decay', () => {
     it('ignores stale timestamps when no decay is applied', () => {
       const now = 1_000_000_000_000;
-      const originalDateNow = Date.now;
-      Date.now = () => now;
 
       const arbiter = setupRelationalComparatorTestGraph();
       arbiter.addNode('user:decay-test', 'user');
@@ -334,16 +332,12 @@ describe('RelationalComparatorRule Tests', () => {
         marginOfSafety: 1.0,
         fallbackBehavior: 'deny'
       });
-      const result = arbiter.check('user:decay-test', 'can_access_decay_test', 'feature:decay-test');
+      const result = arbiter.check('user:decay-test', 'can_access_decay_test', 'feature:decay-test', { now });
       assert.equal(result.possibility, 1);
-
-      Date.now = originalDateNow;
     });
     it('keeps comparison crisp even for older timestamps', () => {
       const arbiter = setupRelationalComparatorTestGraph();
       const now = 1_000_000_000_000;
-      const originalDateNow = Date.now;
-      Date.now = () => now;
 
       arbiter.addNode('user:usage-test', 'user');
       arbiter.addNode('service:limited', 'service');
@@ -383,10 +377,8 @@ describe('RelationalComparatorRule Tests', () => {
         comparator: '<=',
         fallbackBehavior: 'deny'
       });
-      const result = arbiter.check('user:usage-test', 'within_quota', 'service:limited');
+      const result = arbiter.check('user:usage-test', 'within_quota', 'service:limited', { now });
       assert.equal(result.possibility, 1);
-
-      Date.now = originalDateNow;
     });
   });