refactor: Fix React Compiler violation in useForkRef

[frankieyan]

Part of #1066.

• File: src/checkbox-field/use-fork-ref.ts
• Violation: React Compiler skipped optimizing this component because one or more React ESLint rules were disabled (Error, line 33): the eslint-disable react-hooks/exhaustive-deps, react-hooks/use-memo on the manual useMemo (keyed on a spread refs array) makes the compiler skip the module.

Steps

1. Reproduce and confirm the violation.
2. Remove the disabled rules and restructure the ref-merging so it is compiler-compatible, per #mismatched-usememo-dependencies. Do not drop the manual useMemo until the violation is gone.
3. Confirm the count dropped; let the hook update the record file.
4. Verify memoization in the compiled output.