fix(e2e): restore MkdirAll in extractTar for archives missing directory entries

The Linux elastic-agent snapshot tar omits explicit directory entries
for some paths (e.g. components/certs/), unlike the macOS archive.
Restore MkdirAll for regular files and symlinks in extractTar only;
extractZip intentionally omits it per PR elastic#4985 review feedback to
catch missing directory entries in zip archives we produce ourselves.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: ycombinator

testing/e2e/agent_download.go

@@ -229,6 +229,11 @@ func extractTar(t *testing.T, r io.Reader, destDir string) extractedPaths {
 				t.Fatalf("failed to create directory %s: %v", path, err)
 			}
 		case mode.IsRegular():
+			// Ensure parent directories exist — some upstream tar archives (e.g. the
+			// Linux elastic-agent snapshot) omit explicit directory entries.
+			if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+				t.Fatalf("failed to create parent directory for %s: %v", path, err)
+			}
 			w, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, mode.Perm())
 			if err != nil {
 				t.Fatalf("failed to create file %s: %v", path, err)
@@ -245,6 +250,9 @@ func extractTar(t *testing.T, r io.Reader, destDir string) extractedPaths {
 				paths.fleetServerBinary = path
 			}
 		case mode.Type()&os.ModeSymlink == os.ModeSymlink:
+			if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+				t.Fatalf("failed to create parent directory for symlink %s: %v", path, err)
+			}
 			if err := os.Symlink(header.Linkname, path); err != nil {
 				t.Fatalf("failed to create symlink %s: %v", path, err)
 			}