feat: add internal/ui prompts + init subcommand

- internal/ui/prompts.go: MultiSelect with huh TUI + WithNonInteractive for tests
- internal/cli/init.go: NewInit cobra command with --from/--no-prompt flags
- internal/cli/init_test.go: TestInitImportWritesCanonical
- internal/cli/root.go: add resolveRoot helper (shared by profile/rollback/show/init)
- go.mod: add github.com/charmbracelet/huh v1.0.0 as direct dep

internal/ui/prompts_test.go

@@ -0,0 +1,18 @@
+package ui
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMultiSelectNonInteractive(t *testing.T) {
+	sel, err := MultiSelect("pick", []string{"a", "b", "c"}, WithNonInteractive([]string{"a", "c"}))
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"a", "c"}, sel)
+}
+
+func TestMultiSelectNonInteractiveInvalidChoice(t *testing.T) {
+	_, err := MultiSelect("pick", []string{"a", "b"}, WithNonInteractive([]string{"z"}))
+	assert.Error(t, err)
+}