fix(campaign): reject duplicate candidate surfaces

[drewstone]

runOptimization previously dispatched repeated surfaceHash values as separate candidate records. That admitted duplicate population rows and made a claimed broad population non-unique. This change validates every proposed surface against the baseline, earlier generations, and the current proposal before candidate dispatch; rejects duplicates with the exact surface hash and generation; keeps repeated measurements explicit through reps; adds same-generation and cross-generation offline tests proving duplicate candidates do not dispatch; updates proposer guidance and existing no-op fixtures to use distinct candidates. Proof on origin/main 0624e26: focused run-optimization test 20 passed; pnpm test 5386 passed, 3 skipped across 389 files (2 skipped); lint, typecheck, example/script typechecks, build, verify:package, and staged gitleaks all pass. No model or paid calls.

[tangletools]

✅ Auto-approved drewstone PR — 968d0ece

This PR was opened by the trusted drewstone account.
The full PR reviewer audit still runs separately and will publish findings if it detects issues.

_{tangletools · auto-approval · reason: drewstone_author · 2026-08-11T00:30:12Z}