fix: 视频记录不再提前清空，启动重置残留的 running 状态 (#18)

真机使用时发现 55066525387 的子目录里有视频文件，界面上「目录」却不可点。
查明是取视频跑到一半程序被重启，videos 表里该商品的记录已被删除、
新记录还没写回，磁盘有文件而库里无记录。

缺陷一：prepareVideoFetch 在开始下载前先做了一次
ReplaceVideos(product.ID, nil, ...)。而 work.Finalize 里本来就有一次
ReplaceVideos(product.ID, records, now)，ReplaceVideos 的语义就是按
product_id 全量替换。前面那次并不能少做任何事，唯一效果是把「文件已下载
但记录已被删」的窗口从零扩大到整个下载过程，任务停止、程序重启和崩溃
都会落进去。删掉它。

原注释说明作者考虑过这个风险，但只防住了登录失效一种情况。

行为变化是期望的：取视频在下载阶段之前失败时，旧的视频记录会保留而不是
被清空。那些文件确实还在磁盘上，「这次没找到视频」由 products.video_status
表达，不该靠删 videos 记录来表达。

缺陷二：进程退出后 download_status / upload_status 仍停留在 running，
但没有任何任务在跑，是个不会自愈的假状态。启动时在同一事务内把这两个字段
的 running 重置为 pending，只动 running，不碰 video_status 和 videos 表。
重置失败只记 Warn，不中断启动。

按负责人要求未对 cmsp.db 做任何手工订正。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LbdtsD3ohhSMy3KPoCgARq

internal/store/product.go

@@ -322,6 +322,39 @@ func (s *Store) UpdateProductStatus(id, videoStatus, downloadStatus, uploadStatu
 	return nil
 }
 
+// ResetRunningStatuses 把上次进程残留的运行中状态改回待处理。
+func (s *Store) ResetRunningStatuses() (int, error) {
+	tx, err := s.db.Begin()
+	if err != nil {
+		return 0, fmt.Errorf("开启重置运行中状态事务失败：%w", err)
+	}
+	defer tx.Rollback()
+
+	downloadResult, err := tx.Exec(`UPDATE products SET download_status = ? WHERE download_status = ?`,
+		DownloadPending, DownloadRunning)
+	if err != nil {
+		return 0, fmt.Errorf("重置下载运行中状态失败：%w", err)
+	}
+	uploadResult, err := tx.Exec(`UPDATE products SET upload_status = ? WHERE upload_status = ?`,
+		UploadPending, UploadRunning)
+	if err != nil {
+		return 0, fmt.Errorf("重置上传运行中状态失败：%w", err)
+	}
+	if err := tx.Commit(); err != nil {
+		return 0, fmt.Errorf("提交重置运行中状态事务失败：%w", err)
+	}
+
+	downloadCount, err := downloadResult.RowsAffected()
+	if err != nil {
+		return 0, fmt.Errorf("读取重置下载状态数量失败：%w", err)
+	}
+	uploadCount, err := uploadResult.RowsAffected()
+	if err != nil {
+		return 0, fmt.Errorf("读取重置上传状态数量失败：%w", err)
+	}
+	return int(downloadCount + uploadCount), nil
+}
+
 // CountResettableNoneProducts 返回当前被标记为「无同款视频」的商品数量。
 func (s *Store) CountResettableNoneProducts() (int, error) {
 	var count int

internal/store/product_test.go

@@ -6,6 +6,76 @@ import (
 	"testing"
 )
 
+func Test重置残留运行中状态只影响运行中字段(t *testing.T) {
+	s := newTestStore(t)
+	items := []Product{
+		{ID: "下载运行中", ItemID: "1", VideoDiagnosis: VideoDiagnosisMissing},
+		{ID: "上传运行中", ItemID: "2", VideoDiagnosis: VideoDiagnosisOK},
+		{ID: "两个都运行中", ItemID: "3", VideoDiagnosis: VideoDiagnosisMissing},
+		{ID: "已完成", ItemID: "4", VideoDiagnosis: VideoDiagnosisOK},
+		{ID: "已失败", ItemID: "5", VideoDiagnosis: VideoDiagnosisMissing},
+		{ID: "待处理", ItemID: "6", VideoDiagnosis: VideoDiagnosisOK},
+		{ID: "none状态", ItemID: "7", VideoDiagnosis: VideoDiagnosisMissing},
+	}
+	if err := s.UpsertProducts(items, "2026-09-03 10:00:00"); err != nil {
+		t.Fatalf("写入商品失败：%v", err)
+	}
+	statuses := map[string]struct{ download, upload string }{
+		"下载运行中":  {DownloadRunning, UploadDone},
+		"上传运行中":  {DownloadDone, UploadRunning},
+		"两个都运行中": {DownloadRunning, UploadRunning},
+		"已完成":    {DownloadDone, UploadDone},
+		"已失败":    {DownloadFailed, UploadFailed},
+		"待处理":    {DownloadPending, UploadPending},
+		"none状态": {"none", "none"},
+	}
+	for id, status := range statuses {
+		if err := s.UpdateProductStatus(id, "", status.download, status.upload, ""); err != nil {
+			t.Fatalf("准备商品 %s 状态失败：%v", id, err)
+		}
+	}
+	if _, err := s.DB().Exec(`INSERT INTO videos (product_id, source_item, status) VALUES ('下载运行中', 'source', 'downloaded')`); err != nil {
+		t.Fatalf("准备视频记录失败：%v", err)
+	}
+
+	changed, err := s.ResetRunningStatuses()
+	if err != nil {
+		t.Fatalf("重置残留运行中状态失败：%v", err)
+	}
+	if changed != 4 {
+		t.Fatalf("应重置 4 个状态字段，实际 %d", changed)
+	}
+
+	want := map[string]struct {
+		download, upload, diagnosis string
+	}{
+		"下载运行中":  {DownloadPending, UploadDone, VideoDiagnosisMissing},
+		"上传运行中":  {DownloadDone, UploadPending, VideoDiagnosisOK},
+		"两个都运行中": {DownloadPending, UploadPending, VideoDiagnosisMissing},
+		"已完成":    {DownloadDone, UploadDone, VideoDiagnosisOK},
+		"已失败":    {DownloadFailed, UploadFailed, VideoDiagnosisMissing},
+		"待处理":    {DownloadPending, UploadPending, VideoDiagnosisOK},
+		"none状态": {"none", "none", VideoDiagnosisMissing},
+	}
+	for id, expected := range want {
+		got, found, err := s.GetProduct(id)
+		if err != nil || !found {
+			t.Fatalf("读取商品 %s 失败：err=%v found=%v", id, err, found)
+		}
+		if got.DownloadStatus != expected.download || got.UploadStatus != expected.upload {
+			t.Fatalf("商品 %s 状态不正确：download=%q upload=%q", id, got.DownloadStatus, got.UploadStatus)
+		}
+		if got.VideoDiagnosis != expected.diagnosis || got.VideoStatus != VideoPending {
+			t.Fatalf("商品 %s 的视频状态被错误改动：diagnosis=%q videoStatus=%q", id, got.VideoDiagnosis, got.VideoStatus)
+		}
+	}
+
+	var videos int
+	if err := s.DB().QueryRow(`SELECT COUNT(*) FROM videos WHERE product_id = '下载运行中'`).Scan(&videos); err != nil || videos != 1 {
+		t.Fatalf("重置不得删除 videos 记录：count=%d err=%v", videos, err)
+	}
+}
+
 func Test老库升级保留商品和本地状态(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "旧版.db")
 	db, err := sql.Open("sqlite", path)