feat: FbuildSerialAdapter should support DTR reset for device reboot

[zackees]

Summary

FbuildSerialAdapter does not support toggling DTR to reset an ESP32 device. When the device is already booted and idle (no serial output), RPC communication fails because the adapter connects to a silent serial port.

Current behavior

• FbuildSerialAdapter.connect() opens the serial connection but does not toggle DTR
• If the device is already booted, there is no output to read
• RPC ping times out → autoresearch incorrectly reports "device not responding"
• The tool then falls through to the GPIO pre-test which also fails → misleading "connect a jumper wire" error

Expected behavior

FbuildSerialAdapter should expose a reset() or toggle_dtr() method that:

1. Asserts DTR (pulls low) for ~100ms
2. De-asserts DTR
3. Waits for device boot output (~3s)

This matches what PySerialAdapter can do via the underlying pyserial dtr property.

Workaround

FastLED/FastLED PR #2260 commit 2168882 adds a workaround in ci/autoresearch/gpio.py that bypasses FbuildSerialAdapter entirely — it opens a raw pyserial connection just to toggle DTR, closes it, then reconnects via the normal adapter. This is fragile and should be replaced once fbuild supports DTR natively.

Proposed API

class FbuildSerialAdapter:
    def reset_device(self, dtr_hold_ms: int = 100, boot_wait_ms: int = 3000) -> None:
        """Toggle DTR to reset the connected device and wait for boot."""
        ...

Or alternatively, add a dtr property setter that maps to the underlying connection.

Related

• feat(esp32-s3): ISR-driven chunked DMA for LCD_CAM SPI and clockless drivers FastLED#2260 — PR with the workaround
• bug: FbuildSerialAdapter 50ms read timeout drops RPC responses #49 — existing serial adapter timing issues