[ryysel]

On some speakers the LED ring or the display is owned by another process: on a VK Capsula Mini the vendor tweaker draws the ring and already knows about AirPlay, but it cannot see what the assistant is doing, so the ring stays dark while the assistant listens, thinks or speaks.

This adds an opt-in -state_command / MARUSYA_STATE_COMMAND: the agent runs the command on every assistant state change and appends the state as its last argument — idle, listening, thinking, speaking, error, disconnected, announcing. The other process draws it however it likes; the agent keeps no opinion about the ring.

Details:

• Show returns at once and runs the command in the background, so a slow command cannot delay audio;
• repeated states are skipped;
• runs are serialised, so listening -> thinking cannot arrive reversed;
• one run is bounded by 3 s;
• arguments are split like -wake_command (no shell);
• off by default, so nothing changes without the flag.

On our Capsula the command is a three-line script that maps states to capsule-ipc AP2 3|4|5 and restores the AirPlay indication on idle, so ring indication for the assistant no longer depends on a local patch.

Tests: internal/indicator/statecmd with a fake runner (argument passed, repeats skipped, empty command, Show does not block), go vet, go test -race ./internal/indicator/..., marusya-agent builds.