Type checking

[samaloney]

PR Description

• Add mypy and pyright type check configuration and CI job
• Update code to pass new CI type check job
• Review narrow/widen some types for Quantities etc just got it pass right now

If we're want to this it would be good to agree and merge sooner rather than later as touches nearly every file.

If we don't want the types inline could move them to stubs files

AI Assistance Disclosure

Help figure out some of the types and specific inline ignores and configuration

AI tools were used for:

• 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.