feat(disk): add disk read/write latency measurement and display

[Rahul2512Chauhan]

Summary

This PR adds support for measuring and displaying disk read and write
latency in the Disk widget.

What’s Added

• Calculates read latency using (read_time / read operations)
• Calculates write latency using (write_time / write operations)
• Latency updates in real time alongside existing read/write throughput
• Displays latency (in ms) inside the read/write panels

Why This Is Needed

Latency is an important metric for understanding disk performance.
Even when throughput looks normal, high latency can indicate slow I/O,
filesystem issues, or aging hardware.
This implements the requested functionality from Issue #6.

Testing

• Verified on macOS that latency values update correctly.
• Tested alongside read/write graph updates.
• No UI regressions found in the Disk widget.

Related Issue

Closes #6

[Rahul2512Chauhan]

All linters, formatters, and type checks pass (just format, just lint, just type).
Ready for review. 👍

[anistark]

Thanks for the PR @Rahul2512Chauhan 🙌🏼

The "Free, Used, Total" line is repeating. Can you also fix that so it only appears once? It's a diff issue(#8) from your PR. But would be great to have it fixed.

[Rahul2512Chauhan]

Hi @anistark 👋

I checked the duplication issue for the Free / Used / Total rows , it happens only on macOS (APFS) because multiple volumes point to the same physical disk and report identical stats.

So I applied filtering only for Darwin, showing just the / mount, while keeping full behaviour on Linux/Windows where partitions are real and distinct.

{
if platform.system() == "Darwin":
mountpoints = ["/"]
}

Before I push the fix , can you please confirm if this OS-specific approach sounds good to you?

Thanks! 🙌
(ig it kinda work idk 🤔)

[anistark]

Before I push the fix , can you please confirm if this OS-specific approach sounds good to you?

Sounds good. Thanks 🙌🏼

[Rahul2512Chauhan]

Thanks @anistark for your guidance 🙌
All checks are passing ready for another review 👍

[anistark]

Thanks @Rahul2512Chauhan