[reckart]

What's in the PR

• Move Sofa attribute type information from Sphinx docstring prefixes into real type annotations
• Widen optional string parameters to Optional[str] in offset-mapping and sofaString APIs
• Annotate the CAS sofa registry as dict[str, Sofa] and the XMI sofa attribute dict as Dict[str, Any]
• Widen Cas sofa property setters and getters to Optional[str] for sofa_string, sofa_mime, sofa_uri; fix sofa_array to return Optional[FeatureStructure] instead of str
• Add ListBase, NonEmptyListBase, and NonEmptyFSListBase static type classes to model UIMA list node hierarchies with proper head/tail features
• Add TYPE_NAME_LIST_BASE constant and _NON_EMPTY_PRIMITIVE_LIST_TYPES type set
• Add TypeGuard functions is_list_fs, is_non_empty_list_fs, is_non_empty_fs_list for static narrowing of list node types
• Wire ListBase and NonEmptyFSListBase dispatch in Type.get_class via _is_subtype_of checks on _NON_EMPTY_PRIMITIVE_LIST_TYPES
• Improve XMI serialization sink parameter from IO to IO[bytes] for type clarity
• Refactor _collect_list_elements to accept Optional[FeatureStructure], return List[Any], and use is_non_empty_list_fs TypeGuard instead of hasattr for list walk termination
• Add Optional import to xmi.py typing imports
• Add return type annotations to all 31 pytest fixtures with -> str, and 2 fixtures returning List[FeatureStructure]
• Add parameter type annotations to pytest fixture parameters in test functions (small_xmi_path, small_typesystem_xml, etc. as str)
• Add parameter type annotations to @pytest.mark.parametrize arguments across test_xmi.py, test_json.py, test_typesystem.py (typesystem_xml, xmi, json_path as str; ann_begin, ann_end as int; overlap, expect_kept as bool; expect_begin, expect_end as Optional[int]; name, rangeTypeName as str; elementType, multipleReferencesAllowed as Optional[str] / Optional[bool])
• Type helper functions _make_fs_list and _fs_list_elements in test_cas.py with signatures using TypeSystem, Optional[FeatureStructure], and List[Optional[FeatureStructure]]
• Refactor _fs_list_elements to use is_non_empty_list_fs() TypeGuard instead of hasattr for list node termination detection
• Add typing imports (List, Optional) and cassis.typesystem imports (FeatureStructure, TypeSystem, is_non_empty_list_fs) to test files

How to test manually

• No specific test procedure

Automatic testing

• PR includes unit tests

Documentation

• PR updates documentation