fix: Avoid init failures

[jooooonas]

Fix init failures by excluding non-constructor fields in env_config_data serialization

• Adds a _constructor_excludes helper in pool.py that recursively builds a Pydantic exclude tree, skipping dataclass fields with init=False and recursing into nested dataclasses, BaseModel instances, mappings, and sequences.
• env_config_data now passes this exclude tree to model_dump before filtering to EnvConfig.model_fields, preventing fields that cannot be passed to constructors from appearing in the serialized output.
• Behavioral Change: model_dump output for nested config objects will now omit init=False fields that were previously included.

^{Macroscope summarized c14c5fa.}