fix(agent): skip site dirs that have bad .pth files

[efiop]

.pth could be model weights or python path configuration files https://docs.python.org/3/library/site.html Running into the former will result in:

Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/isolate/connections/_local/agent_startup.py", line 45, in <module>
    load_pth_files()
  File "/usr/local/lib/python3.11/site-packages/isolate/connections/_local/agent_startup.py", line 31, in load_pth_files
    site.addsitedir(site_dir)
  File "<frozen site>", line 236, in addsitedir
  File "<frozen site>", line 188, in addpackage
  File "<frozen codecs>", line 322, in decode
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 128: invalid start byte

So we are now just skipping such dirs. There is a risk that we might miss some useful pth files, but I doubt there will ever be a situation where two are mixed.

[Copilot]

Pull Request Overview

This pull request addresses an issue with .pth files by adding error handling in site directory loading.

• Introduces a try/except block around site.addsitedir to skip problematic directories.
• Adds traceback and error notification output for debugging purposes.

[Copilot]

Consider using a logging framework instead of print and traceback for error reporting. This change would improve log aggregation and production diagnostics.