Implement report system and fix template task filtering

- Fix template task filtering bug: templates now hidden from all reports
  except 'template' and 'all' reports, even when using custom filters
- Add support for status:template filter to explicitly show templates
- Implement comprehensive report system with 12 predefined reports:
  * active - Started tasks
  * all - All tasks including templates
  * completed - Completed tasks
  * list - Pending tasks (default)
  * minimal - Pending tasks in minimal format
  * newest - Most recent pending tasks
  * oldest - Oldest pending tasks
  * overdue - Overdue tasks
  * ready - Tasks ready to work on
  * recurring - Pending recurring instances
  * template - Recurring template tasks
  * waiting - Hidden/waiting tasks
- Replace list command with report-based architecture
- Add configurable default_report option (defaults to 'list')
- Add minimal display format (ID + description only)
- Support flexible syntax: 'opal <report> [filters]' or 'opal [filters] <report>'
- Add 'opal reports' command to list all available reports

opal-task/internal/engine/display.go

@@ -11,10 +11,35 @@ import (
 
 // FormatTaskList formats a list of tasks for display
 func FormatTaskList(tasks []*Task, ws *WorkingSet) string {
+	return FormatTaskListWithFormat(tasks, ws, "table")
+}
+
+// FormatTaskListWithFormat formats a list of tasks with specified format
+func FormatTaskListWithFormat(tasks []*Task, ws *WorkingSet, format string) string {
 	if len(tasks) == 0 {
 		return "No tasks found."
 	}
 
+	// Minimal format: just ID and description
+	if format == "minimal" {
+		result := ""
+		for i, task := range tasks {
+			displayID := i + 1
+			if ws != nil {
+				// Use working set display ID if available
+				for id, uuid := range ws.byID {
+					if uuid == task.UUID {
+						displayID = id
+						break
+					}
+				}
+			}
+			result += fmt.Sprintf("%3d %s\n", displayID, task.Description)
+		}
+		return result
+	}
+
+	// Table format (default)
 	t := table.NewWriter()
 
 	// Configure style