- Replace single-sample CPU calculation with two-sample delta method
- Add 0.5 second sleep between CPU stat samples to calculate actual usage
- Parse all 7 CPU time fields (user, nice, sys, idle, iowait, irq, softirq) from /proc/stat
- Calculate CPU percentage as (1 - idle_diff/total_diff) * 100
- Add zero division protection when total_diff is 0
- Fix incorrect CPU usage reporting caused by using cumulative stat values