test(lease): bound persistence-lease tests so a hanging mutant fails instead of wedging the run

[willytop8]

Every test in test/persistence-lease.test.js waited on real filesystem locking with no time bound. Several mutation-contract mutants remove the guard that lets one of those waits finish, so the test does not fail — it hangs the whole run until CI's job timeout, reporting nothing about which mutant caused it.

Found by running npm run test:mutation on Node 24, which had never been done: CI runs the mutation contract only in the Node 22 Quality and package contracts job. On Node 24 it wedged at mutant 28, and after that at mutant 36 in a different test.

• File-local test wrapper applying a 30s timeout to all 31 tests. Node 18 has no --test-timeout, so it cannot be a CLI flag. Generous on purpose: normal runs finish in milliseconds.
• Early-exit race on the child-process test, so a holder that dies before signalling READY fails immediately with the child's stderr instead of blocking forever.
• t.after() reaps the child: finally does not run when a test times out, and a surviving child keeps its stdio pipes — and the whole runner process — alive after the suite ends.

Test-only. No shipped file changes.

Not a product bug. The lease code fails closed correctly and immediately (ERR_GOAL_PERSISTENCE_LEASE_PATH); only the test harness hung.

Checks

Node	suite	mutation
18.20.8	356/356	67/67
20.20.2	356/356	67/67
22.22.3	356/356	67/67
24.19.0	356/356	67/67 — completes for the first time