feat: intermediate chain condition steps, graph-version cache invalidation, rolling-hash chain keys; fix vacuous rigor invariants

Chain intermediates (rule-based reachability):
- ChainRule: a condition step ({ rule, conditionStep }) at an INTERMEDIATE
  position is now EXPANDED from the current node — the rule's base edges'
  destinations, filtered by its defeaters/requirements — and traversal
  continues from each discovered node. Adds _expandRuleFromSrc / direct /
  logical(union/intersection) / defeasible / nested-chain expansion.
- RuleEvaluator: _subjectIsObject flag for unary predicate calls whose subject
  entity IS the object parameter (trusted(other) inside peer_trusted(user,
  other)); previously only subject-var unary calls (_subjectAsObject) were
  handled, so object-var unary defeaters never fired.

Graph-version cache invalidation:
- Arbiter gains a monotonic _graphVersion, incremented on every relation
  mutation. ChainRule result cache, RuleEvaluator rule-result cache, and
  DecisionCache rule cache now stamp entries with the graph version and treat
  any mismatch as a miss — graph mutations can no longer serve stale
  chain/authorization results.

Rolling-hash cache keys:
- UnifiedKeyManager.createChainKey now builds a 53-bit rolling hash (dual
  FNV-1a lanes, exact for ints/floats/strings/nested configs) instead of
  JSON.stringify — no string allocation or serialization on the chain-cache
  hot path. Composite keys stay structured strings because the direct-check
  cache pattern-invalidates by relation ID.

Rigor invariant migration (correctness):
- All 43 rigor test files' throw-based invariants ({ error, errorMessage } =>
  !error && !errorMessage) never saw fn throws — vacuous. Migrated to
  ({ actual }) => actual !== undefined, which fails on any thrown violation
  while passing legitimate null-skips. The migration immediately surfaced
  two latent bugs, now fixed:
    * node-manager/graph-indices skip paths returned bare undefined (falsy
      sentinel) — return { skipped: true }.
    * complex-graph-values-crucible expiry section rewrote values equal to the
      mutation loop's last write; the engine (by design) keeps the old
      timestamp on same-value rewrites so the pre-expiry grant never
      materialized. Now writes guaranteed-different values.

tests/rigor/complex-graph-values-crucible.test.js

@@ -125,10 +125,15 @@ describe('Complex-graph value/comparator crucibles (rigor)', () => {
       }
 
       // TTL-EXPIRY-ON-COMPARATOR: both operands past TTL -> deny, mirror agrees.
+      // Use values NOT in VALUE_SET (137 > 30): the engine keeps the OLD
+      // timestamp when a rewrite does not change the value, so a value equal
+      // to whatever the mutation loop last wrote would NOT refresh freshness
+      // and the pre-expiry grant would (correctly) not materialize. Writing
+      // guaranteed-different values forces a timestamp refresh.
       const kExp = keys[keys.length - 1];
       engineNow = BASE_NOW + 2_000_000;
-      write(kExp, 'balance', 100);
-      write(kExp, 'price', 50);
+      write(kExp, 'balance', 137);
+      write(kExp, 'price', 30);
       if (checkAt(kExp).normal !== 1) fail(`[expiry] pre-expiry grant missing (seed=${seed})`);
       engineNow += TTL + 1;
       const expired = checkAt(kExp);
@@ -149,9 +154,9 @@ describe('Complex-graph value/comparator crucibles (rigor)', () => {
         ))
       ],
       rigor.crucible([
-        rigor.invariant('comparator-parity', ({ error, errorMessage }) => !error || !String(errorMessage).startsWith('[parity]')),
-        rigor.invariant('value-mutation', ({ error, errorMessage }) => !error || !String(errorMessage).startsWith('[mutation]')),
-        rigor.invariant('ttl-expiry-on-comparator', ({ error, errorMessage }) => !error || !String(errorMessage).startsWith('[expiry]'))
+        rigor.invariant('comparator-parity', ({ actual }) => actual !== undefined),
+        rigor.invariant('value-mutation', ({ actual }) => actual !== undefined),
+        rigor.invariant('ttl-expiry-on-comparator', ({ actual }) => actual !== undefined)
       ])
     ).run({ effort: 200, seed: 'complex-graph-values-crucible', artifacts: { dir: '', persist: 'never' } });