Add flat button appearance and light-control-surface colors Ports the contrast/flat-button fix already applied in RotatingSky (a fork of this same template) so it becomes the default for every new sim forked from here. Adds controlSurfaceColorProperty/controlSurfaceDisabledColorProperty/ controlSurfaceTextColorProperty to SimColors.ts for future ComboBox/ NumberDisplay contrast, and a new src/common/SimButtonOptions.ts with flat appearance-strategy bundles (FLAT_RECTANGULAR_BUTTON_OPTIONS, FLAT_RESET_ALL_BUTTON_OPTIONS, FLAT_PLAY_PAUSE_STEP_BUTTON_OPTIONS, TIME_CONTROL_SPEED_RADIO_OPTIONS, SIM_COMBO_BOX_OPTIONS), applied to the template's ResetAllButton and illustrated in the commented-out example button. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_018svZaRUmD44JWTQJLUYdmx - #14