hwModelString

A pretty lowercase rendering of the hardware model: underscores → dashes, version markers <digit>p<digit> → <digit>.<digit> (e.g. RAK4631_V1P0 → rak4631-v1.0). Returns null when the model is unset. The version-marker substitution is constrained to digit-p-digit so model names containing a literal 'p' (e.g. HELTEC_WIRELESS_PAPER) are preserved correctly.