test(execution): add unit tests for code_interpreter tool (#4520)

[mrveiss]

Closes #4520

Summary

• 33 tests in autobot-backend/tools/code_interpreter_test.py
• Covers: stdout/stderr capture, exit codes, unicode, truncation at 10KB, timeout, OS errors, temp file cleanup, LLM schema structure, subprocess args

Test Status

✅ 33/33 passing

[github-actions]

✅ SSOT Configuration Compliance: Passing

🎉 No hardcoded values detected that have SSOT config equivalents!