feat(control_plane): apply light standby hardware policy

components/platform/include/platform.h

@@ -301,6 +301,13 @@ esp_err_t platform_read_firmware_version(char *out, size_t out_len);
 esp_err_t platform_stepper_rotate_angle_with_accel_timeout(float angle,
                                                            int target_delay_us,
                                                            int timeout_ms);
+/**
+ * @brief Release stepper holding current with bounded lock acquisition.
+ *
+ * A negative timeout is invalid, zero is non-blocking, and a positive value
+ * bounds the wait for an in-progress movement to finish.
+ */
+esp_err_t platform_stepper_release_hold(int timeout_ms);
 void platform_stepper_power_off(void);
 
 typedef enum {
@@ -425,6 +432,13 @@ esp_err_t platform_multimodal_audio_start_uplink(
 esp_err_t platform_multimodal_audio_stop_uplink(int timeout_ms);
 bool platform_multimodal_audio_is_uplink_running(void);
 bool platform_multimodal_audio_is_initialized(void);
+/**
+ * @brief Gate the speaker power amplifier without stopping microphone capture.
+ *
+ * Disabling first mutes the codec output and then powers down the speaker PA.
+ * Enabling restores the PA while leaving output muted until playback resumes.
+ */
+esp_err_t platform_multimodal_audio_set_speaker_output_enabled(bool enabled);
 /**
  * @brief Register the single mono PCM observer for the active capture path.
  *