Implements process.threadCpuUsage() to return the current thread's CPU usage, matching Node.js behavior.
Platform-specific implementations:
- macOS: Uses mach_thread_self() and thread_info()
- Linux: Uses getrusage(RUSAGE_THREAD) or getrusage(RUSAGE_LWP) as fallback
- Windows: Uses libuv's uv_getrusage_thread()
Returns an object with user and system CPU time in microseconds, and supports an optional previous value parameter to calculate the difference.
Fixes issue #23890🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
