Refactor installation and runner scripts for enhanced usability and security

- Updated the installation script to clarify that production wrappers do not include fixed test secrets, improving user guidance for local testing.
- Modified the jiggablend-manager and jiggablend-runner scripts to remove fixed test configurations, emphasizing the use of local test credentials via `make init-test`.
- Enhanced error handling in the runner script to ensure that an API key is provided, improving security and user feedback.
- Added new flags and options for the runner, including sandboxing capabilities and GPU ray tracing control, enhancing flexibility for users.
- Improved README documentation to reflect changes in usage and configuration, ensuring users have clear instructions for setup and execution.

internal/runner/workspace/archive.go

@@ -128,6 +128,20 @@ func ExtractTarStripPrefix(reader io.Reader, destDir string) error {
 			if err := os.MkdirAll(filepath.Dir(targetPath), 0755); err != nil {
 				return err
 			}
+			// Reject absolute or escaping symlink targets so extraction cannot
+			// plant links that point outside destDir.
+			linkTarget := header.Linkname
+			if linkTarget == "" {
+				return fmt.Errorf("invalid empty symlink target in tar: %s", header.Name)
+			}
+			if filepath.IsAbs(linkTarget) {
+				return fmt.Errorf("absolute symlink target not allowed in tar: %s -> %s", header.Name, linkTarget)
+			}
+			resolvedLink := filepath.Clean(filepath.Join(filepath.Dir(targetPath), linkTarget))
+			cleanDest := filepath.Clean(destDir)
+			if resolvedLink != cleanDest && !strings.HasPrefix(resolvedLink, cleanDest+string(os.PathSeparator)) {
+				return fmt.Errorf("symlink target escapes extract root: %s -> %s", header.Name, linkTarget)
+			}
 			os.Remove(targetPath) // Remove existing symlink if present
 			if err := os.Symlink(header.Linkname, targetPath); err != nil {
 				return err

internal/runner/workspace/archive_test.go

@@ -24,6 +24,25 @@ func createTarBuffer(files map[string]string) *bytes.Buffer {
 	return &buf
 }
 
+func TestExtractTarStripPrefix_RejectsEscapingSymlink(t *testing.T) {
+	destDir := t.TempDir()
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	// Top-level prefix like Blender archives
+	_ = tw.WriteHeader(&tar.Header{Name: "blender-x/", Typeflag: tar.TypeDir, Mode: 0755})
+	_ = tw.WriteHeader(&tar.Header{
+		Name:     "blender-x/evil",
+		Typeflag: tar.TypeSymlink,
+		Linkname: "../../outside",
+		Mode:     0777,
+	})
+	_ = tw.Close()
+
+	if err := ExtractTarStripPrefix(&buf, destDir); err == nil {
+		t.Fatal("expected escaping symlink to be rejected")
+	}
+}
+
 func TestExtractTar(t *testing.T) {
 	destDir := t.TempDir()