CALIBRATE command captures per-subcarrier CSI amplitudes over a timed
window and stores the averaged baseline in NVS. PRESENCE command enables
real-time scoring via normalized Euclidean distance against the baseline,
with rolling window averaging and 10s holdoff on state transitions.
New commands: CALIBRATE [3-60|STATUS|CLEAR], PRESENCE [ON|OFF|THRESHOLD]
New NVS keys: bl_amps (blob), bl_nsub, presence, pr_thresh
New STATUS fields: presence=, pr_score=
New events: calibrate=done, presence=0|1
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