Improve --filterNaN

[slimbuck]

This PR:

• updates the NaN/infinite filter to keep valid data:
  • opacity range is actually -inf...inf (which maps to 0...1 respectively)
  • scale range includes -inf (which maps to 0), inf is invalid.

[Copilot]

Pull Request Overview

This PR fixes the NaN/infinite value filter to preserve valid infinite values for specific data columns. The filter now correctly handles opacity and scale columns which have legitimate infinite value mappings.

• Updates the filterNaN case to allow negative infinity for opacity and scale columns
• Adds positive infinity support for opacity columns
• Replaces generic object iteration with column-specific filtering logic

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