Extract class FuzzSpec

[tothtamas28]

Refactors the contract fuzzing pipeline around two new named tuple types, Signature and FuzzSpec.

Signature (in contract.py)

Replaces direct use of Method objects throughout the fuzzing pipeline. A Signature captures only the information needed to fuzz a method (its contract name, function name, and argument types) and owns the logic that was previously spread across free functions:

• get_arg_types becomes the private Signature._extract_arg_types
• argument_strategy becomes Signature.argument_strategy()
• A new qualified_name property replaces repeated f'{...contract_name}.{...name}' formatting

FuzzSpec (in skribe.py)

Groups the KORE template pattern and the tuple of Signatures produced from a contract into a single value. A new create_spec method on Skribe produces it, and create_template_pattern is extracted as a helper. The dict property on FuzzSpec serializes the data structure.

Other cleanup

• KORE template setup is pulled out of run_test into create_template_pattern, so run_test now takes a ready Pattern instead of a KAST config + substitution pair
• Imports are converted to relative throughout
• src/tests/ is excluded from the source distribution

[bbyalcinkaya]

Looks good to me.