fix: add nolint:errcheck comments for intentionally unchecked errors

Add //nolint:errcheck comments to intentionally unchecked error returns:

- defer X.Close() calls: errors from closing read-only resources, rows
  after iteration, files, response bodies, and gzip readers are not
  actionable and don't affect correctness

- defer tx.Rollback(): standard Go pattern where rollback after
  successful commit returns an error, which is expected behavior

- defer stmt.Close(): statements are closed with their transactions

- Cleanup operations: DeleteRevision on failure and os.RemoveAll for
  temp directories are best-effort cleanup

- HTTP response encoding: if JSON encoding fails at response time,
  there's nothing useful we can do

- Test/benchmark code: unchecked errors in test setup/cleanup where
  failures will surface through test assertions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/homemanager/indexer.go

@@ -97,7 +97,7 @@ func (idx *Indexer) IndexRevision(ctx context.Context, revision string) (*option
 	if err != nil {
 		return nil, fmt.Errorf("failed to open options.json: %w", err)
 	}
-	defer optionsFile.Close()
+	defer optionsFile.Close() //nolint:errcheck // read-only file
 
 	opts, err := nixos.ParseOptions(optionsFile)
 	if err != nil {
@@ -125,7 +125,7 @@ func (idx *Indexer) IndexRevision(ctx context.Context, revision string) (*option
 	// Store options
 	if err := idx.storeOptions(ctx, rev.ID, opts); err != nil {
 		// Cleanup on failure
-		idx.store.DeleteRevision(ctx, rev.ID)
+		_ = idx.store.DeleteRevision(ctx, rev.ID) //nolint:errcheck // best-effort cleanup
 		return nil, fmt.Errorf("failed to store options: %w", err)
 	}
 
@@ -169,7 +169,7 @@ func (idx *Indexer) buildOptions(ctx context.Context, ref string) (string, func(
 	}
 
 	cleanup := func() {
-		os.RemoveAll(tmpDir)
+		_ = os.RemoveAll(tmpDir) //nolint:errcheck // best-effort temp dir cleanup
 	}
 
 	// Build options.json using nix-build
@@ -286,7 +286,7 @@ func (idx *Indexer) getCommitDate(ctx context.Context, ref string) (time.Time, e
 	if err != nil {
 		return time.Time{}, err
 	}
-	defer resp.Body.Close()
+	defer resp.Body.Close() //nolint:errcheck // response body read-only
 
 	if resp.StatusCode != http.StatusOK {
 		return time.Time{}, fmt.Errorf("GitHub API returned %d", resp.StatusCode)
@@ -345,7 +345,7 @@ func (idx *Indexer) IndexFiles(ctx context.Context, revisionID int64, ref string
 	if err != nil {
 		return 0, fmt.Errorf("failed to download tarball: %w", err)
 	}
-	defer resp.Body.Close()
+	defer resp.Body.Close() //nolint:errcheck // response body read-only
 
 	if resp.StatusCode != http.StatusOK {
 		return 0, fmt.Errorf("download failed with status %d", resp.StatusCode)
@@ -356,7 +356,7 @@ func (idx *Indexer) IndexFiles(ctx context.Context, revisionID int64, ref string
 	if err != nil {
 		return 0, fmt.Errorf("failed to create gzip reader: %w", err)
 	}
-	defer gz.Close()
+	defer gz.Close() //nolint:errcheck // gzip reader read-only
 
 	tr := tar.NewReader(gz)
 	count := 0

internal/homemanager/indexer_test.go

@@ -70,7 +70,7 @@ func TestResolveRevision(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to create store: %v", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // benchmark/test cleanup
 
 	indexer := NewIndexer(store)
 
@@ -104,7 +104,7 @@ func TestGetChannelName(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to create store: %v", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // benchmark/test cleanup
 
 	indexer := NewIndexer(store)
 
@@ -144,7 +144,7 @@ func BenchmarkIndexRevision(b *testing.B) {
 	if err != nil {
 		b.Fatalf("Failed to create store: %v", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // benchmark/test cleanup
 
 	ctx := context.Background()
 	if err := store.Initialize(ctx); err != nil {
@@ -157,7 +157,7 @@ func BenchmarkIndexRevision(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		// Delete any existing revision first (for repeated runs)
 		if rev, _ := store.GetRevision(ctx, TestHomeManagerRevision); rev != nil {
-			store.DeleteRevision(ctx, rev.ID)
+			_ = store.DeleteRevision(ctx, rev.ID) //nolint:errcheck // benchmark cleanup
 		}
 
 		result, err := indexer.IndexRevision(ctx, TestHomeManagerRevision)
@@ -186,7 +186,7 @@ func TestIndexRevision(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to create store: %v", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // benchmark/test cleanup
 
 	ctx := context.Background()
 	if err := store.Initialize(ctx); err != nil {