Add missing @beartype to active_flag_option

[adamtheturtle]

Summary

• Add @beartype decorator to active_flag_option which was the only function in targets.py missing it

Test plan

• Run existing test suite to verify no regressions

🤖 Generated with Claude Code

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Note

Low Risk
Tiny, localized change that only adds runtime type checking to a CLI option helper; low chance of regressions beyond surfacing incorrect caller types.

Overview
Adds @beartype to active_flag_option in src/vws_cli/options/targets.py, making its allow_none: bool argument enforce runtime type checking consistent with the other option decorator helpers.

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