deepmerge has no patched release upstream for GHSA-gcqx-w48m-w2h4. Patch
deepmerge@4.3.1 to reject __proto__ keys by name in mergeObject() across
index.js, dist/cjs.js, and dist/umd.js (TehShrike/deepmerge#274), and
ignore GHSA-gcqx-w48m-w2h4 in auditConfig.
Also use recentTimestamp() across checkDepsStatus.test.ts so mocked
sub-second mtimes never land on an exact second when Date.now() % 1000 === 0.