Traversal without unique() never terminates on cycles (OOMs test suite) #10

Problem

TraversalQuery.toArray() only consults visited when .unique() is set (src/query/TraversalQuery.ts:235). Without .unique() and without maxDepth, any cycle makes the BFS queue grow forever.

Repro:

const g = new GraphDatabase(':memory:');
const x = g.createNode('T', {}), y = g.createNode('T', {});
g.createEdge(x.id, 'CYC', y.id); g.createEdge(y.id, 'CYC', x.id);
g.traverse(x.id).out('CYC').toArray(); // never returns

With maxDepth(6) it returns 6 rows for 2 distinct nodes and re-includes the start node.

Impact

• tests/unit/TraversalQuery.test.ts OOMs at ~4 GB (the fixture has an F→C cycle; tests at lines 288, 321, 382 call toArray() without maxDepth).
• tests/integration/graph-operations.test.ts times out.
• Masked by CI || true (separate issue).

Expected

Non-unique traversal keeps returning a node once per distinct path (test should work without unique() - allow duplicates), but must not revisit a node already on the current path. That terminates on every finite graph.

Benchmark report: 2026-11-02, Apple M2 Pro, Node 22, at a7f9ea7.