refactor: deduplicate optional variable checks

[tomatotomata]

Summary

Extract the duplicated pipe-splitting lookup used for optional target variable groups in CheckVariables into a small groupSatisfied helper. The summary and verbose paths now share the same implementation, preserving the existing behavior while reducing maintenance surface.

Closes #779

Validation

• go test -count=1 ./internal/doctor
• go vet ./internal/doctor
• gofmt -w internal/doctor/doctor.go
• git diff --check
• Divisor council review: Architect, Tester, and Guard all approved.

The repository's full go test -race command could not run locally because this Windows environment has no C compiler for cgo. The change is a pure refactor and the targeted package tests pass.

I used AI assistance for this small refactor and reviewed the repository's AI tooling and contribution guidance.

[marcusburghardt]

Hi @tomatotomata , thanks for the contribution. What are your plans to continue on this PR? After rebasing it, the failed CI will likely pass.

[tomatotomata]

I rebased the one-file refactor locally onto current upstream main (6abc690) as ad8e148, without conflicts.

The focused checks on the rebased tree pass:

• go test -count=1 ./internal/doctor
• go vet ./internal/doctor
• gofmt -d internal/doctor/doctor.go
• git diff --check

The implementation is unchanged apart from the rebased parent, so the failed CI should be worth rerunning against this history. Let me know what you think about the rebased result.

[marcusburghardt]

LGTM