Fix battery charger fault decoding

[TobiasRoeddiger]

Summary:

• Correct the nRF5340 GPIO offsets so the charger CD pin is actually pulsed
• Verify CD high/low levels, charger-current configuration, and safety-timer clearing
• Decode VIN, battery overcurrent, temperature, VINDPM, reset, and timer states
• Separate resettable conditions from electrical faults that require a safe stop
• Make TWIM failures identify NACKs and stuck bus lines, and always issue STOP on errors
• Clean up and resume the target after setup failures or Ctrl-C
• Detect stalled recovery, enforce timeout/reset limits, and reject unsafe polling values
• Preserve charger temperature monitoring and document recovery behavior

Testing:

• 28 unit tests: python3 -m unittest discover -s tools/battery -p "test_*.py" -v
• python3 -m py_compile tools/battery/battery_debug.py tools/battery/test_battery_debug.py
• python3 tools/battery/battery_debug.py recover --help
• Missing-probe CLI failure path
• git diff --check

Hardware validation:

• Not run in this pass because no J-Link probe is connected.

[github-actions]

Build output available:
openearable_v2_firmware.elf.zip
openearable_v2_fota.zip

[github-actions]

Build output available:
openearable_v2_firmware.elf.zip
openearable_v2_fota.zip

[github-actions]

Build output available:
openearable_v2_firmware.elf.zip
openearable_v2_fota.zip