Typing NDCube

[samaloney]

PR Description

Add types and type checking to NDCube

• Some of the types could probably use astropy's QuantityLike
• Some of the types weren't clear so had to guess
• Found some real or at least potential bugs (commit e1808f4)

AI Assistance Disclosure

AI tools were used for:

• [x ] Code generation (e.g., when writing an implementation or fixing a bug)
• [ ] Test/benchmark generation
• [ ] Documentation (including examples)
• [x ] Research and understanding
• [ ] No AI tools were used

Regardless of AI use, the human contributor remains fully responsible for correctness, design choices, licensing compatibility, and long-term maintainability.

[samaloney]

Not sure how to resolve the doc build issue I think its because there is more then one slice object so it can be uniquely resolved?

[DanRyanIrish]

Suggested change

	elements = [f"{', '.join(table.names or ())} ({axes}) {table.physical_types}: {table}"
	elements = [f"{', '.join(table.names) if table.names else ()} ({axes}) {table.physical_types}: {table}"