Summary

• align parallel_task schema and runtime validation around 2-32 independent foreground branches
• harden generate_object arguments, root JSON Schema handling, and active generation deadlines
• replace prose-based retry classification with typed transport and retry-exhaustion errors
• synchronize Node error types and English documentation with the runtime contracts

Validation

• cargo test -p a3s-code-core --lib: 2569 passed, 0 failed, 17 ignored
• cargo test -p a3s-code-core with all features: passed
• cargo clippy --all-targets --all-features -- -D warnings: passed
• cargo fmt --all -- --check: passed
• npm run test:types: passed
• live k3-agent contract probe: root refs, nested values, arrays, enums, and three concurrent child sessions passed