fix: handle TypeError in lookup_class_name for Diagram

[dimitri-yatsenko]

Summary

Fixes intermittent TypeError when generating diagrams with dj.Diagram(schema).

Problem

dj.Diagram(schema) could fail with:

TypeError: '_ClassNamespace' object is not iterable

This occurred when inspect.getmembers() encountered modules containing objects with non-standard __bases__ attributes (like _ClassNamespace from typing internals).

Root Cause

In lookup_class_name(), only ImportError was caught:

try:
    nodes.append(dict(context=dict(inspect.getmembers(member)), ...))
except ImportError:  # TypeError not caught!
    pass

Fix

Catch TypeError in addition to ImportError:

except (ImportError, TypeError):
    pass  # could not inspect module members, skip

Impact

• No behavior change for working cases
• Fixes edge cases where unusual modules (typing, metaclasses) are in context
• Defensive fix - just skips problematic modules and continues search

Closes

• dj.ERD(schema) runs into TypeError #1072

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