Closes the same gap as the AVR / RP2040 commits — qemu-lcgamboa's UART
transmits the byte over the WebSocket as a 'serial_output' event with no
GPIO toggle, so an oscilloscope on the ESP32 TX pin saw nothing while
real silicon would render the 8N1 frame at the configured baud rate.
Two changes inside Esp32Bridge:
* New `onPinChangeWithTime: (pin, state, timeMs) => void` callback
that hooks the oscilloscope at parity with AVRSimulator /
RP2040Simulator. The 'gpio_change' event now also flows through it
(timestamped with `performance.now()` — QEMU virtual time isn't
surfaced across the wire, but at 1× sim speed the wall-clock skew
is invisible on any practical sweep). This also fixes the broader
issue that ESP32 boards previously couldn't show ANY digital GPIO
activity on the scope.
* `emitUartTxFrame(byte, uart)` synthesizes start + 8 data LSB-first
+ stop transitions at `this.uartBaudRate` (default 115200) on the
UART0 TX pin, mapped per board variant:
esp32 / esp32-devkit-c-v4 / esp32-cam / wemos-lolin32-lite: GPIO1
esp32-s3 / xiao-esp32-s3 / arduino-nano-esp32: GPIO43
esp32-c3 / xiao-esp32-c3 / aitewinrobot-esp32c3-supermini: GPIO21
Backend doesn't expose the live baud rate so we default to 115200
(the Arduino default). Override path: bridge.uartBaudRate = N
once we surface Serial.begin's argument via a backend event.
Wire-up: `bridge.onPinChangeWithTime = getOscilloscopeCallback(boardId)`
inside the three Esp32Bridge construction sites in useSimulatorStore
(setBoardType, addBoard, changeBoard).
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