Add SR_LIVE=1 environment variable to switch SimBridge from test mode
to TCP connection. Default behavior unchanged (test mode).
- sim_bridge.gd: read SR_LIVE env var instead of hardcoded test_mode
- game_state.gd: find player entity by kind.variant == "Player" instead
of hardcoded entity_id 1 (real server assigns different IDs)
- Makefile: add 'make game' (builds server, starts it, launches client
with SR_LIVE=1, kills server on exit) and 'make stop' helper
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>