Counter reader: IPC, cache misses, branch mispredicts

[codingwithmagga]

Description

Implement a counter reader that retrieves collected hardware counter values and exposes them as structured metrics.

Acceptance Criteria

• IPC is correctly derived from instructions / cycles
• L1/L2/L3 cache miss counts and rates are exposed
• Branch misprediction rate is calculated and accessible
• Values are consistently readable after a defined measurement interval

Notes

TDD — tests are written before implementation code.