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/config.go

@@ -13,6 +13,7 @@ import (
 type Config struct {
 	DefaultFilter  string `mapstructure:"default_filter"`
 	DefaultSort    string `mapstructure:"default_sort"`
+	DefaultReport  string `mapstructure:"default_report"`
 	ColorOutput    bool   `mapstructure:"color_output"`
 	WeekStartDay   string `mapstructure:"week_start_day"`
 	DefaultDueTime string `mapstructure:"default_due_time"`
@@ -83,6 +84,7 @@ func LoadConfig() (*Config, error) {
 	// Set defaults
 	v.SetDefault("default_filter", "status:pending")
 	v.SetDefault("default_sort", "due,priority")
+	v.SetDefault("default_report", "list")
 	v.SetDefault("color_output", true)
 	v.SetDefault("week_start_day", "monday")
 	v.SetDefault("default_due_time", "")
@@ -131,6 +133,7 @@ func SaveConfig(cfg *Config) error {
 
 	v.Set("default_filter", cfg.DefaultFilter)
 	v.Set("default_sort", cfg.DefaultSort)
+	v.Set("default_report", cfg.DefaultReport)
 	v.Set("color_output", cfg.ColorOutput)
 	v.Set("week_start_day", cfg.WeekStartDay)
 	v.Set("default_due_time", cfg.DefaultDueTime)