Fix SIGBUS crash on macOS ARM64 by removing unsafe pointer extraction

[cbjuan]

Summary

• Remove unsafe __extract_env__() method that caused memory corruption across different compiled modules
• Add clone() method to PyBaseEnv for safe environment cloning via Python interface
• Add PyBaseEnvWrapper for external Rust environments (like GridWorld) that extend PyBaseEnv
• Fixes BUG: SIGBUS crash during RLSynthesis.learn() on macOS ARM #35

Description

Problem

When external packages like qiskit-gym statically link TwisteRL and create their own Rust environments, calling evaluate() or collect() would cause a SIGBUS crash (exit code 138) on macOS ARM64. This happened even with num_cores=1, ruling out parallelism as the cause. The root cause was the unsafe pointer extraction pattern in __extract_env__() which cast raw pointers between different compilation units with incompatible vtable layouts.

Solution

• Remove unsafe pointer extraction - Delete extract_env() method entirely
• Add clone() method to PyBaseEnv - Uses dyn_clone::clone_box() to safely clone the internal Rust environment. This method is inherited by ALL PyBaseEnv subclasses, including external ones like GridWorld.
• Add PyBaseEnvWrapper - A new wrapper for external Rust environments that:
• Uses PyBaseEnv-compatible method names (step, reward, reset)
• Clones via the new clone() method
• Detects interface type by checking for step vs next methods
• Keep PyEnvImpl - For pure Python environments with custom interface (next, value, copy)

[cbjuan]

After the last release of qiskit-gym https://pypi.org/project/qiskit-gym/0.2.0/, this issue does not appear anymore. Closing this PR for now