Wire five new WebSocket frames into hub.go: setCalibration (client→hub),
calibration (hub→client broadcast), reloadConfig (client→hub), configSaved and
configReloaded (hub→client acks with ok/path/error). Extend hubCmd with cal
field, add buildCalibrationMsg and buildConfigAckMsg builders, send calibration
on client connect, and run Save/Reload on separate goroutines to avoid blocking
the Run() select loop.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Finding 1: strip trailing [digits] array-element suffix from Signal so one
calibration entry covers an entire array signal, matching the C++ strchr
truncation and the JS equivalent.
Finding 2: after the 16-byte Unit truncation, drop any trailing partial UTF-8
rune so json.Marshal never emits replacement characters; keeps byte limit in
sync with C++ strncpy(u, unit, kMaxUnitLen).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
