Fix arg-type, return-value, and assignment mypy errors

[bizfsc]

Fix arg-type, return-value, assignment, return, index, and operator mypy errors across the codebase.

Changes

canopen/nmt.py

• Use bytes() instead of list[int] for send_message() and send_periodic() calls.
• Use b'' instead of None for node guarding remote frame data.

canopen/emcy.py

• Fix wait() return type: Optional[EmcyError] (was EmcyError, but returns None on timeout).

canopen/network.py

• Fix add_node() return type to Union[RemoteNode, LocalNode] (accepts both).
• Fix create_node() parameter type to Union[int, LocalNode].
• Add assert node.id is not None for index safety.
• Add type: ignore[arg-type] for node construction where OD may be None.

canopen/variable.py

• Add raise ValueError at end of read() to satisfy missing return.
• Annotate Bits.raw with proper type.
• Add isinstance check for value_descriptions dict access.
• Add type: ignore for dynamically typed operations (decode_phys, decode_desc, encode_bits).

canopen/sdo/base.py

• Add explicit return None in get_variable().
• Add type: ignore[return-value] for SdoArray.__len__().

canopen/objectdictionary/__init__.py

• Fix __getitem__ dot-notation access with isinstance check for indexability.
• Add explicit return None in get_variable().
• Annotate ODVariable.parent and ODArray.parent with proper Union types.
• Fix decode_phys() return type to Union[int, float].
• Rewrite encode_phys() without intermediate division.
• Add type: ignore for encode_raw string operations and min/max comparisons.
• Add type: ignore for dest.close() and source.name in file handling.

Impact

Reduces mypy error count from 95 to 51 (standalone), and combined with PRs #647, #649, #650 will bring the count down significantly further.",
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[codecov]

Codecov Report

❌ Patch coverage is 88.57143% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
canopen/objectdictionary/__init__.py	88.88%	1 Missing and 1 partial ⚠️
canopen/variable.py	75.00%	2 Missing ⚠️

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