Implement opal-task Phases 6-8: Complete CLI Implementation

Phase 6: Display and Basic Commands
- Add display.go with colored formatting for tasks, projects, tags
- Implement cmd/root.go with Cobra command structure
- Implement cmd/list.go for listing and filtering tasks
- Implement cmd/add.go with support for regular and recurring tasks
- Implement cmd/done.go with bulk completion and confirmation

Phase 7: Advanced Commands
- Implement cmd/modify.go for updating task attributes
- Implement cmd/delete.go with soft delete confirmation
- Implement cmd/start.go and cmd/stop.go for task timing
- Implement cmd/count.go for counting filtered tasks
- Implement cmd/projects.go and cmd/tags.go for aggregation

Phase 8: Integration and Polish
- Update main.go to use CLI commands
- Add colored output with fatih/color
- Format task lists with proper alignment
- Highlight overdue tasks in red, upcoming in yellow
- Test end-to-end workflow: add, list, done, recurring tasks
- Verify recurrence spawning works correctly

All CLI commands functional and tested!

opal-task/cmd/root.go

@@ -0,0 +1,57 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+
+	"git.jnss.me/joakim/opal/internal/engine"
+	"github.com/spf13/cobra"
+)
+
+var rootCmd = &cobra.Command{
+	Use:   "opal",
+	Short: "Opal task manager - taskwarrior-inspired CLI task management",
+	Long: `Opal is a powerful command-line task manager inspired by taskwarrior.
+It supports filtering, tags, priorities, projects, and recurring tasks.`,
+	Run: func(cmd *cobra.Command, args []string) {
+		// Default behavior: show pending tasks
+		if err := listTasks(args); err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+	},
+}
+
+func Execute() error {
+	return rootCmd.Execute()
+}
+
+func init() {
+	cobra.OnInitialize(initializeApp)
+
+	// Add subcommands
+	rootCmd.AddCommand(addCmd)
+	rootCmd.AddCommand(listCmd)
+	rootCmd.AddCommand(doneCmd)
+	rootCmd.AddCommand(modifyCmd)
+	rootCmd.AddCommand(deleteCmd)
+	rootCmd.AddCommand(startCmd)
+	rootCmd.AddCommand(stopCmd)
+	rootCmd.AddCommand(countCmd)
+	rootCmd.AddCommand(projectsCmd)
+	rootCmd.AddCommand(tagsCmd)
+}
+
+func initializeApp() {
+	// Initialize database
+	if err := engine.InitDB(); err != nil {
+		fmt.Fprintf(os.Stderr, "Error initializing database: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Load config
+	if _, err := engine.LoadConfig(); err != nil {
+		fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
+		os.Exit(1)
+	}
+}