Context

The current BME280 driver (src/sensors/BME280Driver.h) uses the RP2040's hardware I2C peripheral via Wire/Wire1. This has two limitations:

1. GPIO constraints — Hardware I2C0/I2C1 only work on specific GPIO pairs (I2C0: 0/1, 4/5, 8/9, 12/13, 16/17, 20/21; I2C1: 2/3, 6/7, 10/11, 14/15, 18/19, 26/27). A PIO-based implementation would work on any GPIO 0-15, keeping the universal slot promise.
2. Library dependency — Uses <Wire.h> which pulls in the Arduino I2C stack. A custom PIO driver would be self-contained and potentially smaller.

Proposal

Implement a PIO-based I2C bit-bang driver for BME280 that:

• Works on any GPIO pair (not just hardware I2C pins)
• Follows the existing driver pattern (async state machine like DS18B20/DHT22)
• Uses the same compensation formulas already implemented
• Has no external library dependency

References

• BME280 datasheet: https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bme280-ds002.pdf
• RP2040 PIO documentation: https://datasheets.raspberrypi.com/pico/raspberry-pi-pico-c-sdk.pdf (Chapter 3)
• Current driver: src/sensors/BME280Driver.h
• Sensor format metadata: src/sensors/SensorHelpers.h (SensorFormat::forType())

Acceptance

• Compiles with SIMUT_SENSOR_BME280=1
• BME280 detected and read on any GPIO 0-15 pair
• No <Wire.h> dependency
• Async reads work alongside DS18B20/DHT22 without blocking
• Flash cost ≤ current driver (~7 KB)