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/database/sqlite.go

@@ -23,7 +23,7 @@ func NewSQLiteStore(path string) (*SQLiteStore, error) {
 
 	// Enable foreign keys
 	if _, err := db.Exec("PRAGMA foreign_keys = ON"); err != nil {
-		db.Close()
+		db.Close() //nolint:errcheck // best-effort cleanup on connection failure
 		return nil, fmt.Errorf("failed to enable foreign keys: %w", err)
 	}
 
@@ -192,7 +192,7 @@ func (s *SQLiteStore) ListRevisions(ctx context.Context) ([]*Revision, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to list revisions: %w", err)
 	}
-	defer rows.Close()
+	defer rows.Close() //nolint:errcheck // rows.Err() checked after iteration //nolint:errcheck // rows.Err() checked after iteration
 
 	var revisions []*Revision
 	for rows.Next() {
@@ -249,7 +249,7 @@ func (s *SQLiteStore) CreateOptionsBatch(ctx context.Context, opts []*Option) er
 	if err != nil {
 		return fmt.Errorf("failed to begin transaction: %w", err)
 	}
-	defer tx.Rollback()
+	defer tx.Rollback() //nolint:errcheck // rollback after commit returns error, which is expected
 
 	stmt, err := tx.PrepareContext(ctx, `
 		INSERT INTO options (revision_id, name, parent_path, type, default_value, example, description, read_only)
@@ -257,7 +257,7 @@ func (s *SQLiteStore) CreateOptionsBatch(ctx context.Context, opts []*Option) er
 	if err != nil {
 		return fmt.Errorf("failed to prepare statement: %w", err)
 	}
-	defer stmt.Close()
+	defer stmt.Close() //nolint:errcheck // statement closed with transaction
 
 	for _, opt := range opts {
 		result, err := stmt.ExecContext(ctx,
@@ -301,7 +301,7 @@ func (s *SQLiteStore) GetChildren(ctx context.Context, revisionID int64, parentP
 	if err != nil {
 		return nil, fmt.Errorf("failed to get children: %w", err)
 	}
-	defer rows.Close()
+	defer rows.Close() //nolint:errcheck // rows.Err() checked after iteration
 
 	var options []*Option
 	for rows.Next() {
@@ -384,7 +384,7 @@ func (s *SQLiteStore) SearchOptions(ctx context.Context, revisionID int64, query
 	if err != nil {
 		return nil, fmt.Errorf("failed to search options: %w", err)
 	}
-	defer rows.Close()
+	defer rows.Close() //nolint:errcheck // rows.Err() checked after iteration
 
 	var options []*Option
 	for rows.Next() {
@@ -422,7 +422,7 @@ func (s *SQLiteStore) CreateDeclarationsBatch(ctx context.Context, decls []*Decl
 	if err != nil {
 		return fmt.Errorf("failed to begin transaction: %w", err)
 	}
-	defer tx.Rollback()
+	defer tx.Rollback() //nolint:errcheck // rollback after commit returns error, which is expected
 
 	stmt, err := tx.PrepareContext(ctx, `
 		INSERT INTO declarations (option_id, file_path, line)
@@ -430,7 +430,7 @@ func (s *SQLiteStore) CreateDeclarationsBatch(ctx context.Context, decls []*Decl
 	if err != nil {
 		return fmt.Errorf("failed to prepare statement: %w", err)
 	}
-	defer stmt.Close()
+	defer stmt.Close() //nolint:errcheck // statement closed with transaction
 
 	for _, decl := range decls {
 		result, err := stmt.ExecContext(ctx, decl.OptionID, decl.FilePath, decl.Line)
@@ -455,7 +455,7 @@ func (s *SQLiteStore) GetDeclarations(ctx context.Context, optionID int64) ([]*D
 	if err != nil {
 		return nil, fmt.Errorf("failed to get declarations: %w", err)
 	}
-	defer rows.Close()
+	defer rows.Close() //nolint:errcheck // rows.Err() checked after iteration
 
 	var decls []*Declaration
 	for rows.Next() {
@@ -501,7 +501,7 @@ func (s *SQLiteStore) CreateFilesBatch(ctx context.Context, files []*File) error
 	if err != nil {
 		return fmt.Errorf("failed to begin transaction: %w", err)
 	}
-	defer tx.Rollback()
+	defer tx.Rollback() //nolint:errcheck // rollback after commit returns error, which is expected
 
 	stmt, err := tx.PrepareContext(ctx, `
 		INSERT INTO files (revision_id, file_path, extension, content, byte_size, line_count)
@@ -509,7 +509,7 @@ func (s *SQLiteStore) CreateFilesBatch(ctx context.Context, files []*File) error
 	if err != nil {
 		return fmt.Errorf("failed to prepare statement: %w", err)
 	}
-	defer stmt.Close()
+	defer stmt.Close() //nolint:errcheck // statement closed with transaction
 
 	for _, file := range files {
 		// Compute metadata if not already set
@@ -561,7 +561,7 @@ func (s *SQLiteStore) GetDeclarationsWithMetadata(ctx context.Context, revisionI
 	if err != nil {
 		return nil, fmt.Errorf("failed to get declarations with metadata: %w", err)
 	}
-	defer rows.Close()
+	defer rows.Close() //nolint:errcheck // rows.Err() checked after iteration
 
 	var decls []*DeclarationWithMetadata
 	for rows.Next() {