fix: system stats calculation and prevent runtime errors

[mdqst]

I've gone through the system stats handling on Linux, Windows, and MacOS and made a few key fixes:

• Linux /proc/stat: Added a check for len(data) < 11 to prevent IndexError on non-standard systems.
• Division by zero: Added if total != 0 else 0.0 wherever idle percentages were calculated.
• Windows: Corrected formula to user + kernel - idle and fixed GetSystemTimes error handling to properly raise WinError().
• MacOS / UTC time: Removed .replace(tzinfo=None) to preserve correct ISO-formatted UTC timestamps.

these changes prevent crashes and ensure that system stats are calculated accurately across platforms.

[rustbot]

r? @jdno

rustbot has assigned @jdno.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[rust-log-analyzer]

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

1 file would be reformatted, 26 files already formatted --- /checkout/src/ci/cpu-usage-over-time.py +++ /checkout/src/ci/cpu-usage-over-time.py @@ -117,7 +117,11 @@ idle = self.idle - prev.idle user = self.user - prev.user kernel = self.kernel - prev.kernel - return float(idle) / float(user + kernel - idle) * 100 if user + kernel - idle != 0 else 0.0 + return ( + float(idle) / float(user + kernel - idle) * 100 + if user + kernel - idle != 0 + else 0.0 + ) elif sys.platform == "darwin": from ctypes import * rerun tidy with `--extra-checks=py:fmt --bless` to reformat Python code tidy error: checks with external tool 'ruff' failed some tidy checks failed Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck` Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/rust-tidy /checkout /checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo /checkout/obj/build 4 /node/bin/npm --extra-checks=py,cpp,js,spellcheck` failed with exit code 1 Created at: src/bootstrap/src/core/build_steps/tool.rs:1561:23 Executed at: src/bootstrap/src/core/build_steps/test.rs:1281:29 Command has failed. Rerun with -v to see more details. Build completed unsuccessfully in 0:01:14 local time: Thu Sep 18 12:43:14 UTC 2025 network time: Thu, 18 Sep 2025 12:43:14 GMT ##[error]Process completed with exit code 1. Post job cleanup.