Add throughput lease registry

[joelteply]

Summary

• add typed ThroughputLease with target_silicon, holder, expiry, cost, and revocation policy
• add pure ThroughputLeaseRegistry with acquire, renew, release, expire, snapshot, and reclaimable queries
• export ts-rs bindings for lease contracts

Validation

• cargo test -p continuum-core --features metal,accelerate cognition::throughput_lease --lib (8 passed)
• cargo test -p continuum-core --features metal,accelerate cognition::adaptive_throughput --lib (14 passed)
• pre-push TypeScript clean
• pre-push Rust compile/tests passed with metal,accelerate

Notes

This is still pure/in-memory. Next Lane B PR can mirror leases into FootprintRegistry and let PressureBroker pick expired/revocable leases before pinned work.