PM-4151: suppress incomplete MM final export data

[jmgasper]

What was broken
Marathon Match submitter exports could show negative failed-run scores, finalScore values while a challenge was still in submission, and a finalRank column before the challenge was completed.

Root cause
The challenge export SQL treated any final score field as exportable regardless of challenge status, used negative review summation scores as normal scores, and always emitted Marathon Match final columns from the formatter.

What was changed
Changed the submitter, valid submitter, and winner SQL to ignore negative Marathon Match scores, only expose finalScore/finalRank data for completed challenges, and avoid falling back to submission.finalScore when a final review row explicitly failed.
Updated the challenge report formatter so Marathon Match finalScore and finalRank columns are only emitted when at least one row has those values.
Updated report descriptions and DTO documentation to match the completed-only final data behavior.

Any added/updated tests
Updated the challenge SQL regression spec for completed-only final scores, negative score filtering, and completed-only final ranks.
Added a service regression test that verifies active Marathon Match exports omit finalScore and finalRank columns when final scoring is unavailable.

Validation
pnpm lint passed.
pnpm test -- --runInBand src/reports/challenges/challenge-export-sql.spec.ts src/reports/challenges/challenges-reports.service.spec.ts passed.
pnpm build passed.
The full pnpm test -- --runInBand suite still fails in unrelated existing SFDC DTO/service specs and report-directory access coverage on the current develop base.