Handle broken repr in tracing

[ShipItAndPray]

Summary

• guard tracing stringification so hook tracing does not break hook execution when traced objects have a broken __repr__/__str__
• keep the fallback output informative by using the default object repr and the original exception
• add a regression test covering broken repr values in traced hook kwargs

Testing

• uv run --python 3.12 pytest testing/test_pluginmanager.py -k broken_repr -q
• uv run --python 3.12 pytest testing/test_pluginmanager.py -q

Closes #424.

[RonnyPfannschmidt]

this is in part ad odds with switching to repr in another pr
also as far as i understood there is a general understanding that str/repr should never fail for object that completed their ctor