Add advanced register control functions (REG0x17-0x1A)
- REG0x17: Add reset(), thermal regulation, converter frequency, and VBUS overvoltage functions
- REG0x18: Add BATFET control functions
- REG0x19: Add peak discharge current, VBAT UVLO, and charge rate functions
- REG0x1A: Add thermistor control functions (ignore, cool/warm current settings)
- Add comprehensive test coverage with enum switch statements in example sketch
- All functions tested with hardware showing correct default values
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
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