Per-tenant rate limits & quotas

[JSONbored]

Problem: Without limits, one customer's loop could consume disproportionate compute or starve others, and a runaway loop has no cap.

Area: Platform

Proposal: Apply per-tenant rate limits and hard resource quotas tied to each tenant's paid/staked allocation from #4792.

Deliverables:

• Enforced per-tenant limits, with a clear, actionable error when a tenant exceeds their quota.

Acceptance criteria:

• A test tenant exceeding its quota is stopped cleanly, with the correct, user-facing explanation of why.
• One tenant exceeding its quota has no observable effect on another tenant's loop.

Boundaries:

• Blocked on Rental ledger integration #4792.

---

Part of #4778.

---

Cross-reference (added after #5669): see #5669 for the reconciliation between this issue and AMS Cloud Readiness's #5223 (Design: per-tenant scheduling and queue-fairness model).

[linear-code]

JSO-3468