add-binding-feature

# Add a Binding Feature Use this skill when a change affects the public runtime surface and must stay in parity across the Rust core, FFI, and one or more bindings. Do not use this skill for: - Internal-only core refactors with no public API change - New middleware contracts, which use the middleware-specific workflow - Binding-local bug fixes that do not change shared behavior - Docs-only or example-only updates ## Implementation Order 1. **Core Rust** Implement the behavior first in `crates/core/src/api/` and related core modules such as `crates/core/src/api/runtime/`, `crates/core/src/codec/`, or `crates/core/src/json.rs`. 2. **FFI / shared C surface, when affected** Update `crates/ffi` and its generated header only when the capability is exposed through the C ABI or Go binding. 3. **Language-native bindings** Update each binding that exposes the capability; leave unrelated bindings unchanged. 4. **Language wrapper helpers** Update Python wrapper modules, Go shorthand packages, typed helpers, or adaptive/plugin helpers if the new behavior belongs there. 5. **Docs and examples** Update reference docs, language-binding docs, and examples when the public surface or expected usage changed. 6. **Validation** Follow the repository validation policy for the surfaces whose public or observable behavior changed. ## Naming Conventions | Layer | Convention | Example | |-------------|--------------...