v0.6.3 — auto-detect human balanced vs firmware reset

Changed

• CC2 speed pinning now tells a human's balanced apart from a firmware
  reset — no more Auto escape hatch. The firmware resets speed_mode to
  balanced as the leading edge of every Canvas filament switch, a few
  seconds before the head parks; measured reset→park lead times are
  tight (6–8 s, never above ~9 s). pycentauri uses that: a drop to
  balanced followed by a park within ~12 s is the firmware and the
  pinned mode is re-applied when the switch completes; a drop that sits
  at balanced for ~12 s with no park is a human tapping balanced on the
  touchscreen, so the pin is released and balanced is honored. A
  sustained non-balanced touchscreen mode is still adopted as the pin
  outright. Both paths live-verified 2026-07-05 (firmware re-apply and
  human release, each with journal-logged decisions).
• Removed the auto speed mode / Auto button. It existed only to
  release the pin for the touchscreen-balanced case, which is now
  detected automatically. speed auto, {"mode": "auto"}, and the web
  UI Auto button are gone.