perf_event_open wrapper for hardware counter collection #10

Description

Encapsulate the Linux perf_event_open syscall as a reusable C++ component that opens, configures, and manages hardware performance counters.

Acceptance Criteria

• Counters can be opened for individual events (e.g. cycles, instructions, cache-misses)
• Errors are handled gracefully for unsupported events or insufficient permissions
• API supports process-scoped and CPU-scoped monitoring
• No direct syscall usage outside of the wrapper in the rest of the codebase

Notes

TDD — tests are written before implementation code.