feat: refactor sgclaw around zeroclaw compat runtime

third_party/zeroclaw/docs/hardware/datasheets/esp32.md

@@ -0,0 +1,22 @@
+# ESP32 GPIO Reference
+
+## Pin Aliases
+
+| alias       | pin |
+|-------------|-----|
+| builtin_led | 2   |
+| red_led     | 2   |
+
+## Common pins (ESP32 / ESP32-C3)
+
+- **GPIO 2**: Built-in LED on many dev boards (output)
+- **GPIO 13**: General-purpose output
+- **GPIO 21/20**: Often used for UART0 TX/RX (avoid if using serial)
+
+## Protocol
+
+ZeroClaw host sends JSON over serial (115200 baud):
+- `gpio_read`: `{"id":"1","cmd":"gpio_read","args":{"pin":13}}`
+- `gpio_write`: `{"id":"1","cmd":"gpio_write","args":{"pin":13,"value":1}}`
+
+Response: `{"id":"1","ok":true,"result":"0"}` or `{"id":"1","ok":true,"result":"done"}`