Main operations: `suggest()`, `popularWords()`, `indexer()`, `createIndexIfNothing()`, `createNextIndex()`, `switchIndex()`, `removeDisableIndices()`

### SuggestIndexer (Indexing Engine)
Location: `src/main/java/org/codelibs/fess/suggest/index/SuggestIndexer.java`

Handles all indexing operations, content parsing, and word management (bad words, elevate words).

### SuggestSettings (Configuration)

/**
 * Internal operations class for core indexing functionality.
 * Handles indexing of SuggestItem objects with bad word filtering.
 *
 * <p>This class is package-private and intended for internal use by SuggestIndexer.
 */
public class IndexingOperations {

    private static final Logger logger = LogManager.getLogger(IndexingOperations.class);

    private final Client client;
    private final SuggestSettings settings;

/**
 * Internal operations class for bad word and elevate word management.
 * Handles adding, deleting, and restoring special words.
 *
 * <p>This class is package-private and intended for internal use by SuggestIndexer.
 */
public class WordManagementOperations {

    private static final Logger logger = LogManager.getLogger(WordManagementOperations.class);

    private final SuggestSettings settings;

/**
 * Internal operations class for deletion functionality.
 * Handles deletion of suggest items by ID, query, or kind.
 *
 * <p>This class is package-private and intended for internal use by SuggestIndexer.
 */
public class DeletionOperations {

    private static final Logger logger = LogManager.getLogger(DeletionOperations.class);

    /** Default page size for scroll operations. */