debug: Add comprehensive channel and state logging

Add detailed debug logging to track all channel operations and state
changes in the webgpu-cube example. This will help diagnose why the
auto-rotate state isn't updating when the toggle button is clicked.

Logging added for:
- Initial state send in App constructor
- Command reception and processing
- State changes (autoRotate, speed, rotation)
- State updates sent to controlState channel
- Controls component state reception
- Button click events
- Render cycles with current state
- app.Update() calls

All logs prefixed with component/operation for easy filtering:
- [Goroutine] - goroutine lifecycle
- [Command] - command details
- [State Change] - variable updates
- [State Send] - state sent to channel
- [State Receive] - state received from channel
- [Controls] - Controls component operations
- [Controls.Render] - render cycle info

This will help identify if:
1. Commands are being received
2. State is being updated
3. State updates are being sent
4. Controls is receiving updates
5. Re-renders are being triggered

Author: claude

examples/webgpu-cube/app_gen.go

@@ -0,0 +1,21 @@
+//go:build js && wasm
+
+package main
+
+import "fmt"
+
+func logCommand(cmd ControlCommand) {
+	log(fmt.Sprintf("[Command] Type: %s, Value: %f", cmd.Type, cmd.Value))
+}
+
+func logStateChange(field string, oldVal, newVal interface{}) {
+	log(fmt.Sprintf("[State Change] %s: %v -> %v", field, oldVal, newVal))
+}
+
+func logStateSend(state ControlState) {
+	log(fmt.Sprintf("[State Send] AutoRotate: %t, Speed: %f", state.AutoRotate, state.Speed))
+}
+
+func logStateReceive(state ControlState) {
+	log(fmt.Sprintf("[State Receive] AutoRotate: %t, Speed: %f", state.AutoRotate, state.Speed))
+}