fix: validate model optimization options

[kholdrex]

Summary

Validate model optimization options before fitting so invalid numerical settings fail fast with clear ArgumentError messages. This prevents silent no-op, non-finite, or unstable configurations from reaching the Rasch, 2PL, and 3PL optimization loops.

Changes

• Add shared optimization option validation for model constructors.
• Reject non-positive or non-finite tolerances and learning rates, invalid decay factors, non-integer iteration counts, and complex/string/nil values.
• Add shared specs covering invalid option values across Rasch, 2PL, and 3PL models.

Test Plan

• RSpec suite passed.
• RuboCop passed with no offenses.
• Gem build passed.