Update geometry types

[cortesi]

Summary

• use u32 and i32 for geom types
• update viewport and widgets to match
• convert backend to use new geometry types
• adjust tests and examples

Testing

• cargo clippy --fix --allow-dirty --examples --tests --all
• cargo test --workspace

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https://chatgpt.com/codex/tasks/task_e_6868ac5111b48333a31babff1c99c513