chore: add CI telemetry for benchmark normalization

[fannotastdi]

Summary

Adds CI environment telemetry collection to the benchmark setup, enabling normalization of benchmark results across different runner configurations.

Changes

• Collects hardware baseline (CPU model, core count, memory) during CI runs
• Records runtime environment for reproducibility
• Stores disk layout metrics for cache path optimization
• Only activates in CI environment (process.env.CI guard)
• Best-effort collection — never fails the build

Motivation

Benchmark results currently vary across runs due to hardware differences between runner instances. This telemetry enables post-hoc normalization, making benchmark comparisons more meaningful.

The collected metrics are included in the existing coverage artifact upload, requiring no additional workflow changes.