refactor: frame converter and mp4 track improvements

- Refactor frame converter implementation
- Update mp4 track to use ICodex
- General refactoring and code improvements

🤖 Generated with [Claude Code](https://claude.ai/code)

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

plugin/debug/pkg/monitor_model.go

@@ -0,0 +1,27 @@
+package debug
+
+import (
+	"database/sql"
+	"time"
+)
+
+// Session 表示一个监控会话
+type Session struct {
+	ID        uint32 `gorm:"primarykey"`
+	PID       int
+	Args      string
+	StartTime time.Time
+	EndTime   sql.NullTime
+}
+
+// Task 表示一个任务记录
+type Task struct {
+	ID                          uint `gorm:"primarykey"`
+	SessionID, TaskID, ParentID uint32
+	StartTime, EndTime          time.Time
+	OwnerType                   string
+	TaskType                    byte
+	Description                 string
+	Reason                      string
+	Level                       byte
+}