fix: 触发器响应优化 — pending trigger 在当前step结束后立即触发

修复网页触发器点击后无响应的问题。原因是 defer_triggers 模式下，
pending trigger 必须等待整个 sequence 播完才触发，当 step 有
random_loop_range [2,15] 时用户可能要等几分钟。
现在改为当前 step 循环结束后立即检查并执行 pending trigger。

同时添加 systemd service 脚本。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/showen_v2.service

@@ -0,0 +1,19 @@
+[Unit]
+Description=ShowenV2 — 数字生命窗口平台
+After=network.target dbus.service
+Wants=network.target
+
+[Service]
+Type=simple
+User=showen
+Environment=DISPLAY=:0
+Environment=XAUTHORITY=/home/showen/.Xauthority
+WorkingDirectory=/home/showen/Showen/ShowenV2
+ExecStart=/home/showen/Showen/ShowenV2/target/release/showen_v2 --config /home/showen/Showen/ShowenV2/configs/dog_state_machine.json
+Restart=on-failure
+RestartSec=3
+StandardOutput=journal
+StandardError=journal
+
+[Install]
+WantedBy=graphical.target

src/plugins/video/state_machine.rs

@@ -50,6 +50,13 @@ impl StateMachine {
             return Ok(false);
         }
 
+        // 有待执行的触发器时，跳过 sequence 剩余 step，立即切换状态
+        if self.pending_trigger_target.is_some() {
+            let target_state = self.pending_trigger_target.take().unwrap();
+            self.transition_to_state(&target_state)?;
+            return Ok(self.current_state != old_state);
+        }
+
         let sequence_len = self
             .current_state_config()
             .ok_or_else(|| anyhow::anyhow!("当前状态不存在: {}", self.current_state))?
@@ -410,16 +417,10 @@ mod tests {
         assert_eq!(machine.current_state, "idle");
         assert_eq!(machine.current_loop_remaining, 1);
 
-        assert!(!machine
-            .on_video_completed()
-            .expect("should advance within same state"));
-        assert_eq!(machine.current_sequence_index, 1);
-        assert_eq!(machine.current_loop_remaining, 1);
-        assert_eq!(machine.current_video_id().as_deref(), Some("tail"));
-
+        // 当前 step 播完后，有 pending trigger 应立即跳转，跳过后续 step
         assert!(machine
             .on_video_completed()
-            .expect("pending trigger should fire at sequence end"));
+            .expect("pending trigger should fire after current step ends"));
         assert_eq!(machine.current_state, "called");
         assert_eq!(machine.current_video_id().as_deref(), Some("called"));
         assert!(!machine.has_pending_trigger());