- Auto-restore (startup) now checks midiThru->start() return value;
  on failure the toggle stays OFF and status shows the missing device
  name instead of falsely claiming "Forwarding ON"
- Add rebuildMidiInputs() (mirroring rebuildMidiOutputs()); called at
  startup and from the Refresh MIDI button so newly-connected devices
  appear without restarting the app; restores previous selection silently
  to avoid spurious onChange/config writes
- Mark Bug 3 (input change doesn't restart forwarding) and Bug 4
  (no SysEx filter in handleIncomingMidiMessage) with TODO comments
  for a later session

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>