fix(test): use hrtime for unique test directories

Replace Date.now() with process.hrtime.bigint() for higher precision
timestamps. Tests were failing because Date.now() has millisecond precision,
causing tests running in quick succession to share the same directory name.

Author: jdalton

test/process-lock.test.ts

@@ -19,9 +19,10 @@ describe('process-lock', () => {
 
   beforeEach(async () => {
     // Create unique test directory for each test.
+    // Use process.hrtime.bigint() for higher precision than Date.now()
     testDir = path.join(
       tmpdir(),
-      `process-lock-test-${Date.now()}-${Math.random().toString(36).slice(2)}`,
+      `process-lock-test-${process.hrtime.bigint()}-${Math.random().toString(36).slice(2)}`,
     )
     lockPath = path.join(testDir, 'test.lock')