fix: resolve remaining errcheck errors in test files

Fixed 4 remaining errcheck violations:
- squashfs_components_test.go:350 - defer f.Close()
- squashfs_test.go:27, 102, 146 - defer sqfs.Close()

All defer Close() calls now properly discard errors using anonymous functions.

All 21 tests continue to pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: MagicalTux

squashfs_components_test.go

@@ -347,7 +347,7 @@ func TestSquashFSNew(t *testing.T) {
 	if err != nil {
 		t.Fatalf("failed to open test file: %s", err)
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 
 	// Create SquashFS using New instead of Open
 	sqfs, err := squashfs.New(f)

squashfs_test.go

@@ -24,7 +24,7 @@ func TestSquashfs(t *testing.T) {
 	if err != nil {
 		t.Fatalf("failed to open testdata/zlib-dev.squashfs: %s", err)
 	}
-	defer sqfs.Close()
+	defer func() { _ = sqfs.Close() }()
 
 	data, err := fs.ReadFile(sqfs, "pkgconfig/zlib.pc")
 	if err != nil {
@@ -99,7 +99,7 @@ func TestBigdir(t *testing.T) {
 	if err != nil {
 		t.Fatalf("failed to open testdata/bigdir.squashfs: %s", err)
 	}
-	defer sqfs.Close()
+	defer func() { _ = sqfs.Close() }()
 
 	t1 := time.Now()
 	data, err := fs.ReadFile(sqfs, "bigdir/99999.txt")
@@ -143,7 +143,7 @@ func TestBigdir(t *testing.T) {
 	if err != nil {
 		t.Fatalf("failed to open testdata/azusa_symlinks.squashfs: %s", err)
 	}
-	defer sqfs.Close()
+	defer func() { _ = sqfs.Close() }()
 
 	_, err = sqfs.FindInode("full/lib64/libLLVMIRReader.a", false)
 	if err != nil {