Add a general court-supervision input variable

## Summary

Add a general person-level input variable for whether a child is under court supervision. The variable should be program-agnostic so Tennessee CCAP and other programs can reuse it instead of defining program-specific inputs.

## Motivation

Tennessee's Child Care Certificate Program extends child eligibility through age 18 for children under court supervision (State Plan §2.2.1(c)). The Tennessee CCAP implementation currently leaves this condition unmodeled rather than introducing a narrow `tn_ccap_under_court_supervision` variable.

## Suggested implementation

- Add a general boolean person-level input such as `is_under_court_supervision`.
- Choose a definition period and metadata consistent with other reusable person-level status inputs.
- Update Tennessee CCAP child eligibility to apply the special-needs age limit when the child is under court supervision.
- Add tests for eligible and over-age court-supervised children.
- Consider whether any other programs can adopt the new input.

## Source

Tennessee CCDF State Plan §2.2.1(c).