feat: canvas drag/resize/selection, modal planner, default OneWay (唐超)

- Canvas: 坐标轴、顶点坐标、框拖拽、角点缩放、点击选中高亮
- 路径规划改为弹窗覆盖层，编辑状态不丢失
- 展开任务状态持久化到 Pinia store
- 扫描模式默认 OneWay
- 保存时 startTime/endTime/durationMinutes 清空为 ""
- exposureTime/frameRate/captureIntervalSeconds 默认 0
- 去除生成航线后的扫描线文字标注

src-tauri/src/io/json_writer.rs

@@ -3,7 +3,27 @@ use crate::error::AppError;
 use crate::models::MissionPlan;
 
 pub fn write_mission(path: &Path, mission: &MissionPlan) -> Result<(), AppError> {
-    let content = serde_json::to_string_pretty(mission)?;
+    // Clear computed timing fields before saving
+    let mut cleaned = mission.clone();
+    for task in &mut cleaned.tasks {
+        task.duration_minutes = 0.0;
+        task.estimated_duration_minutes = 0.0;
+        task.start_time = Some("".to_string());
+        task.end_time = Some("".to_string());
+        for sub in &mut task.sub_tasks {
+            sub.duration_minutes = 0.0;
+            sub.estimated_duration_minutes = 0.0;
+            sub.start_time = Some("".to_string());
+            sub.end_time = Some("".to_string());
+            if sub.capture_interval_seconds.is_none() { sub.capture_interval_seconds = Some(0); }
+            if sub.exposure_time.is_none() { sub.exposure_time = Some(0); }
+            if sub.frame_rate.is_none() { sub.frame_rate = Some(0); }
+        }
+    }
+    let content = serde_json::to_string_pretty(&cleaned)?;
+    let content = content
+        .replace("\"durationMinutes\": 0.0", "\"durationMinutes\": \"\"")
+        .replace("\"estimatedDurationMinutes\": 0.0", "\"estimatedDurationMinutes\": \"\"");
     std::fs::write(path, content)?;
     Ok(())
 }