feat: harden workspace file APIs

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/workspace/manager_test.go

@@ -0,0 +1,51 @@
+package workspace
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestLocalManagerListReturnsSortedWorkspaces(t *testing.T) {
+	mgr := NewLocalManager(t.TempDir())
+	if _, err := mgr.Create("beta"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := mgr.Create("alpha"); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := mgr.List()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 2 {
+		t.Fatalf("len = %d, want 2", len(got))
+	}
+	if got[0].ID != "alpha" || got[1].ID != "beta" {
+		t.Fatalf("ids = %q, %q; want alpha, beta", got[0].ID, got[1].ID)
+	}
+	if got[0].Root == "" || got[1].Root == "" {
+		t.Fatal("manager list should keep internal roots for service use")
+	}
+}
+
+func TestLocalManagerListSkipsUnsafeDirectoryNames(t *testing.T) {
+	root := t.TempDir()
+	if err := os.Mkdir(filepath.Join(root, "valid"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	// Contains space, which is invalid per ValidID regex
+	if err := os.Mkdir(filepath.Join(root, "bad name"), 0755); err != nil {
+		t.Fatal(err)
+	}
+
+	mgr := NewLocalManager(root)
+	got, err := mgr.List()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 1 || got[0].ID != "valid" {
+		t.Fatalf("got %#v, want only valid", got)
+	}
+}