fix: initialize g_hooks before using it

[not-matthias]

No description provided.

[Copilot]

Pull Request Overview

This PR fixes a bug where measurement_is_instrumented() was being called before measurement_init() initialized the required g_hooks variable. The fix reorders initialization to ensure g_hooks is set up before use.

• Moved measurement_init() to the beginning of the constructor
• Changed member initialization from initializer list to constructor body
• Added a clarifying comment about the initialization order requirement

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[codspeed-hq]

CodSpeed Performance Report

Merging #28 will not alter performance

_{Comparing cod-1547-codspeed-cpp-fix-unknown-environment-warnings-when-running (7c8c06d) with main (4a4951f)}

Summary

✅ 152 untouched