Get high-resolution timestamp.
Prefers Node.js hrtime if available, otherwise falls back to Date.now().
Note: Bun's Bun.ns provides nanosecond precision but requires the Bun runtime.
For cross-runtime compatibility, we use hrtime (Node) or Date.now().
Get high-resolution timestamp. Prefers Node.js hrtime if available, otherwise falls back to Date.now(). Note: Bun's Bun.ns provides nanosecond precision but requires the Bun runtime. For cross-runtime compatibility, we use hrtime (Node) or Date.now().