Add hot reload for development

Implement automatic rebuild and browser reload during development:

- File watcher monitors .go files for changes with configurable extensions
- Builder compiles Go source to WASM on file changes
- LiveReload WebSocket server notifies connected browsers to reload
- DevServer combines all components for easy development setup
- HTML injection adds reload script automatically

Usage:
  dev := host.NewDevServer("public", "index.html", ".", "public/app.wasm")
  dev.ListenAndServe(":8080")

Closes #9

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

host/README.md

@@ -36,9 +36,9 @@ myapp/
 
 The server serves files from the specified public directory. Any request path maps directly to files:
 
-- `/` → `public/index.html`
-- `/app.wasm` → `public/app.wasm`
-- `/styles.css` → `public/styles.css`
+- `/` -> `public/index.html`
+- `/app.wasm` -> `public/app.wasm`
+- `/styles.css` -> `public/styles.css`
 
 **SPA Fallback**: Unknown paths and directories fall back to `index.html`, enabling client-side routing.
 
@@ -68,28 +68,109 @@ Gzip compression is automatically applied to compressible content types when the
 
 Binary assets (PNG, JPEG, etc.) are served uncompressed since they're already compressed.
 
-## Development vs Production
+## Hot Reload (Development)
 
-### Development
+The `DevServer` provides automatic rebuild and browser reload during development:
+
+```go
+package main
+
+import (
+	"git.flowmade.one/flowmade-one/iris/host"
+)
+
+func main() {
+	// Create dev server with hot reload
+	dev := host.NewDevServer(
+		"public",       // Static files directory
+		"index.html",   // Index file
+		".",            // Source directory to watch
+		"public/app.wasm", // WASM output path
+	)
+	
+	// Start watching and serving
+	dev.ListenAndServe(":8080")
+}
+```
+
+### How It Works
+
+1. **File Watcher**: Monitors `.go` files in the source directory for changes
+2. **Auto Build**: Runs `GOOS=js GOARCH=wasm go build` when changes are detected
+3. **Browser Reload**: Injects a WebSocket client into HTML pages that triggers reload on build success
+
+### Directory Structure for Development
+
+```
+myapp/
+├── main.go             # WASM application entry point
+├── server/
+│   └── main.go         # Dev server (code above)
+└── public/
+    ├── index.html
+    ├── app.wasm        # Generated by dev server
+    └── wasm_exec.js
+```
+
+### Workflow
+
+1. Start the dev server: `go run ./server`
+2. Open `http://localhost:8080` in your browser
+3. Edit your Go source files
+4. Save - the browser automatically reloads with your changes
+
+### Custom Watch Configuration
+
+```go
+// Watch additional file types
+watcher := host.NewWatcher(
+	".",
+	onChangeCallback,
+	host.WithExtensions(".go", ".html", ".css"),
+	host.WithInterval(100*time.Millisecond),
+)
+```
+
+### Manual Components
+
+For advanced use cases, you can use the individual components:
+
+```go
+// File watcher
+watcher := host.NewWatcher(".", func() {
+	log.Println("Files changed")
+})
+watcher.Start()
+defer watcher.Stop()
+
+// WASM builder
+builder := host.NewBuilder(".", "public/app.wasm")
+result := builder.Build()
+if result.Success {
+	log.Println("Build succeeded")
+}
+
+// Live reload (WebSocket notifications)
+lr := host.NewLiveReload()
+http.Handle("/__livereload", lr)
+lr.NotifyReload() // Triggers reload in all connected browsers
+```
+
+## Production
+
+For production, use the standard `Server` instead of `DevServer`:
 
 ```go
 func main() {
 	server := host.New("public", "index.html")
-	http.ListenAndServe(":8080", server)
+	log.Fatal(http.ListenAndServe(":8080", server))
 }
 ```
 
-Run with:
-```bash
-go run server.go
-```
-
-### Production
-
-For production, compile the server and run as a binary:
+Compile and deploy:
 
 ```bash
-go build -o server ./server.go
+go build -o server ./server
 ./server
 ```