test(patch): tighten single.go unit coverage

Replace overlapping package-type tests in single_test.go with focused single-arch coverage and move the unique parsePkgTypes edge cases into patch_validation_test.go. Strengthen loader error assertions, add setupWorkingFolder failure coverage, and cover report parsing plus no-updates guardrails before BuildKit is involved.

Coverage achieved on single.go: 67.4%.

New test functions:
- TestSetupWorkingFolderReturnsTempDirCreationError
- TestSetupWorkingFolderReturnsEnsurePathErrors
- TestPatchSingleArchImageReturnsReportParseError
- TestPatchSingleArchImageReturnsNoUpdatesFoundAfterFiltering

Strengthened test:
- TestLoadImageToRuntimeReturnsLoaderCreationErrors now verifies io.PipeReader CloseWithError propagation

No production code changed.

Signed-off-by: Omer <omer@descope.com>

Author: omercnet

pkg/patch/patch_validation_test.go

@@ -108,12 +108,24 @@ func TestParsePkgTypes(t *testing.T) {
 			expected:    []string{utils.PkgTypeOS, utils.PkgTypeLibrary},
 			expectError: false,
 		},
+		{
+			name:        "duplicates are preserved in order",
+			input:       "library,library,os",
+			expected:    []string{utils.PkgTypeLibrary, utils.PkgTypeLibrary, utils.PkgTypeOS},
+			expectError: false,
+		},
 		{
 			name:        "invalid type",
 			input:       "invalid",
 			expected:    nil,
 			expectError: true,
 		},
+		{
+			name:        "blank entry is rejected",
+			input:       "os,,library",
+			expected:    nil,
+			expectError: true,
+		},
 		{
 			name:        "mixed valid and invalid types",
 			input:       "os,invalid",