feat: per-key hint highlighting, no default forward command, rename roulade to roll in UI and internals

feat: HUD UX pass - state label with slot-machine roll, keycap hints, per-device highlighting, quack sound from the runtime

feat: gamepad support mirroring the robot runtime mapping

feat: one-shot roulade on Space with auto-return to walk, drop reset button

fix: propagate private-space __sign JWT to all same-origin requests

feat: infinite shader grid, edge-anchored UI, drop hero title

feat: standalone Microduck RL playground (MuJoCo WASM + ONNX policies)

initial commit