Single LED (P0.28) doubles as heartbeat, message flash, shutdown flash
and LoRa TX indicator, all sharing the same physical pin. Adds one PWM
channel on that pin (heartbeat-pwm-led/lora-tx-pwm-led aliases) and a
single 0-100 brightness knob (get/set led) covering every one of those
events at once, deliberately RAM-only: resets to a 10% default on every
reboot regardless of CLI changes made in a previous session. The
existing persisted on/off gate (set leds on|off) is untouched.
Boards without heartbeat-pwm-led/lora-tx-pwm-led aliases keep their
current plain-GPIO behavior unchanged.
ZephCore T096