feat: all six CLI commands (new, list, resume, open, info, archive)

Complete command implementations with all flags per spec. Shared query resolution helper.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/open.go

@@ -0,0 +1,44 @@
+package cmd
+
+import (
+	"fmt"
+	"path/filepath"
+	"time"
+
+	"github.com/spf13/cobra"
+	"github.com/warrenronsiek/ctask/internal/config"
+	"github.com/warrenronsiek/ctask/internal/shell"
+	"github.com/warrenronsiek/ctask/internal/workspace"
+)
+
+var openCmd = &cobra.Command{
+	Use:   "open <query>",
+	Short: "Open a workspace directory without launching the agent",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runOpen,
+}
+
+var openAll bool
+
+func init() {
+	openCmd.Flags().BoolVarP(&openAll, "all", "a", false, "Include archived workspaces in query resolution")
+	rootCmd.AddCommand(openCmd)
+}
+
+func runOpen(cmd *cobra.Command, args []string) error {
+	root := config.ResolveRoot()
+	ws := resolveOne(root, args[0], openAll)
+
+	// Update updated_at
+	now := time.Now().UTC().Truncate(time.Second)
+	ws.Meta.UpdatedAt = now
+	metaPath := filepath.Join(ws.Path, "task.yaml")
+	if err := workspace.WriteMeta(metaPath, ws.Meta); err != nil {
+		return fmt.Errorf("updating metadata: %w", err)
+	}
+
+	envVars := config.EnvVars(ws.Meta.Slug, ws.Meta.Mode, root, ws.Path, ws.Meta.Category)
+
+	// Spawn interactive subshell (not agent, not cd in parent)
+	return shell.ExecShell(ws.Path, envVars, ws.Meta.Slug, ws.Meta.Mode)
+}