Persist managed worker replay payloads

[jaikoo]

Summary

• persist prepared worker lease payloads with the exact task result and harness events before posting
• replay persisted result/events after restart so completion retry does not re-run task execution
• keep compatibility with legacy lease-only recovery files

Test Plan

• cd rust && cargo fmt --all -- --check && cargo clippy --workspace --all-targets -- -D warnings && cargo test --workspace