feat: add Node.js napi-rs binding and Express integration

Uses napi-rs over FFI or WASM because it compiles Rust directly into a
native .node addon, bypassing the C ABI entirely (JS↔Rust vs
JS→C→Rust→C→JS). Buffer for protocol data is zero-copy from V8 backing
store. No manual memory management (V8 ref-counting vs webui_free()).
WASM exists already for browser/universal use but is ~1.5-3x slower
than native for CPU-bound rendering.

Add webui-node crate that compiles the WebUI handler into a native
Node.js addon via napi-rs, exposing a render(html, dataJson) function.

Add Express integration example at examples/integration/node-express
following the same patterns as hyper and tiny_http (--app CLI arg,
routes for /, /assets/*, /hmr, file watcher for HMR).

- New crate: crates/webui-node (napi-rs cdylib with 10 unit tests)
- New integration: examples/integration/node-express (ESM, Express 5)
- Add napi/napi-derive/napi-build to workspace dependencies
- Add ISC license to deny.toml allowlist (napi transitive dep)
- Add node-express to xtask INTEGRATION_BUILDS
- Update DESIGN.md and README.md

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: mohamedmansour

Cargo.lock

@@ -4,6 +4,7 @@ members = [
     "crates/webui-expressions",
     "crates/webui-ffi",
     "crates/webui-handler",
+    "crates/webui-node",
     "crates/webui-parser",
     "crates/webui-protocol",
     "crates/webui-state",
@@ -31,6 +32,8 @@ tokio = { version = "1.49.0", features = ["full"] }
 clap = { version = "4", features = ["derive"] }
 console = "0.15"
 prost = "0.13"
+napi = { version = "3", features = ["napi4"] }
+napi-derive = "3"
 wasm-bindgen = "0.2"
 serde-wasm-bindgen = "0.6"
 
@@ -42,6 +45,7 @@ tokio-test = "0.4.5"
 
 # Build dependencies
 prost-build = "0.13"
+napi-build = "2"
 
 [profile.release]
 lto = true

Cargo.toml

@@ -477,6 +477,7 @@ webui/
 │   ├── webui-expressions/    # Expression evaluation engine
 │   ├── webui-ffi/            # C-compatible FFI bindings
 │   ├── webui-handler/        # Protocol handler implementation
+│   ├── webui-node/           # Node.js native addon (napi-rs)
 │   ├── webui-parser/         # HTML/CSS/template parser
 │   ├── webui-protocol/       # Protocol definition
 │   ├── webui-state/          # State management

DESIGN.md

@@ -80,6 +80,24 @@ The interactive playground runs WebUI in the browser via WebAssembly. The WASM o
 cargo xtask build-wasm
 ```
 
+### Integration Examples
+
+The `examples/integration/` directory contains ready-to-run server examples:
+
+```bash
+# Run with Rust + hyper (async, HTTP/1.1 + HTTP/2)
+cargo xtask run hyper hello-world
+
+# Run with Rust + tiny_http (synchronous, lightweight)
+cargo xtask run tiny_http hello-world
+
+# Run with Node.js + Express (napi-rs native addon)
+cargo build -p webui-node
+cd examples/integration/node-express && npm ci && node src/index.js --app hello-world
+```
+
+Each integration serves the app on `http://127.0.0.1:8080/` with hot-reload file watching.
+
 ## Contributing
 
 This project welcomes contributions and suggestions.  Most contributions require you to agree to a

README.md

@@ -0,0 +1,25 @@
+[package]
+name = "webui-node"
+description = "Node.js native addon for WebUI framework via napi-rs"
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+repository.workspace = true
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+napi = { workspace = true }
+napi-derive = { workspace = true }
+webui-parser = { path = "../webui-parser", default-features = false }
+webui-handler = { path = "../webui-handler" }
+webui-protocol = { path = "../webui-protocol" }
+serde_json = { workspace = true }
+
+[build-dependencies]
+napi-build = { workspace = true }
+
+[dev-dependencies]
+webui-test-utils = { path = "../webui-test-utils" }