[BUG] Hard crash due to Mac System Integrity Protection (SIP) Security Protocol Activation

**Affects:** PythonCall

**Describe the bug**
Setting the `PYTHON_JULIACALL_HANDLE_SIGNALS` environment variable manually and then importing `juliacall` triggers the disk security protocol on MacOS

Meanwhile just importing `juliacall` works fine

ANY VERSIONS

Reproduce script:
```py
import os

os.environ["PYTHON_JULIACALL_HANDLE_SIGNALS"] = os.environ.get("PYTHON_JULIACALL_HANDLE_SIGNALS", "yes")

import juliacall
```

For clarity: importing `juliacall` works fine, but if you set environment variable first, it triggers SIP

**Your system**
Please provide detailed information about your system:
- MacOS
- Any versions

**Additional context**
First seen at https://github.com/MilesCranmer/PySR/issues/682

Start with the reproduction script and the juliacall import path, then trace how PYTHON_JULIACALL_HANDLE_SIGNALS is handled on macOS. Done means importing juliacall with that environment variable set no longer triggers the reported SIP security protocol activation.

由索引模型根據 Issue 內容生成。