test(quota): preserve unknown-fraction and genuine exhaustion contracts

[diegosouzapw]

Summary

Reconcile the legacy domain suite with #14276 (282e2c4, Jan Leon). A zero total or nonfinite percentage is an unknown quota fraction, not authoritative exhaustion. Assert that those cases neither block account selection nor produce a display observation. Keep the known zero-percent case blocking even with an invalid reset date.

No production code, policy, baseline or timeout changes.

Evidence

• Exact base 373c31f reproduces the stale threshold assertion.
• Updated domain suite plus original unknown-limit/Vertex-spend regressions: 12 PASS, zero failures/skips. Includes real exhaustion, 429 preservation and persistence/rehydration.
• Prettier, ESLint with existing frozen suppressions, diff check and full branch hooks passed.

Draft recovery slice, not full-candidate acceptance. Preserves the original fix and contributor attribution.

[diegosouzapw]

Fechando como coberta pela #14511, mergeada na release/v3.8.51 (drenou as mesmas base-reds: genérico de stdio do auggie, imports do projectCombo, strip de _native*Passthrough e os guards de catálogo/prefixo/qwen/opencode/quota). O conteúdo que só esta PR tinha já entrou pelas #14501, #14503, #14508 e #14516. (merge-batch 2026-09-24)