Document the setInput/pressButton -> physical button mapping where agents look,
so the genesis_plus_gx inversion (and the fact every other core is straight-
through) is discoverable at the platform level, not just in tool descriptions.

- Every platform MENTAL_MODEL gets a 'Driving input over MCP' subsection.
  The 3 gpgx platforms (Genesis/SMS/GG) flag the INVERSION with a mapping table
  (setInput({a}) presses Genesis C / SMS button 2, not A/button 1). The other 11
  state 'straight through, no surprise'. Atari 7800 documents the 1-button-default
  / 2-button-mode footgun; C64 + Atari 2600 note single-fire via b/south.
- genesis/sms/gg TROUBLESHOOTING gain an 'I drive with setInput but the action
  button doesn't fire' entry (where a stuck agent searches).
- AGENTS.md 'Cross-platform inputs' gains the inversion warning + the
  spatial-names/pressButton safe-habit guidance, summarizing the 14-platform audit.

All spatial-name claims cross-checked against FACE_BUTTON_MAP. 563/563 green.