[model-gateway] change sgl-router to sgl-model-gateway (#14312)

sgl-model-gateway/examples/wasm/wasm-guest-ratelimit/README.md

@@ -0,0 +1,68 @@
+# WASM Rate Limit Example for sgl-router
+
+This example demonstrates rate limiting middleware for sgl-router using the WebAssembly Component Model.
+
+## Overview
+
+This middleware provides rate limiting:
+
+- **Default**: 60 requests per minute per identifier
+- **Identifier Priority**: API Key > IP Address > Request ID
+- **Response**: Returns `429 Too Many Requests` when limit exceeded
+
+**Important**: This is a simplified demonstration. Since WASM components are stateless, each worker thread maintains its own counter. For production, implement rate limiting at the router/host level with shared state.
+
+## Quick Start
+
+### Build and Deploy
+
+```bash
+# Build
+cd examples/wasm-guest-ratelimit
+./build.sh
+
+# Deploy (replace file_path with actual path)
+curl -X POST http://localhost:3000/wasm \
+  -H "Content-Type: application/json" \
+  -d '{
+    "modules": [{
+      "name": "ratelimit-middleware",
+      "file_path": "/absolute/path/to/wasm_guest_ratelimit.component.wasm",
+      "module_type": "Middleware",
+      "attach_points": [{"Middleware": "OnRequest"}]
+    }]
+  }'
+```
+
+### Customization
+
+Modify constants in `src/lib.rs`:
+
+```rust
+const RATE_LIMIT_REQUESTS: u64 = 100; // requests per window
+const RATE_LIMIT_WINDOW_MS: u64 = 60_000; // time window in ms
+```
+
+## Testing
+
+```bash
+# Send multiple requests (first 60 succeed, then 429)
+for i in {1..65}; do
+  curl -s -o /dev/null -w "%{http_code}\n" \
+    http://localhost:3000/v1/models \
+    -H "Authorization: Bearer secret-api-key-12345"
+done
+```
+
+## Limitations
+
+- Per-instance state (not shared across workers)
+- No cross-process state sharing
+- Memory growth with unique identifiers
+- State lost on instance restart
+
+## Troubleshooting
+
+- Verify module attached to `OnRequest` phase
+- Check identifier extraction logic matches request format
+- Note: Each WASM worker has separate counter