Index all text files under a local folder for retrieval.

Reads supported text files recursively, splits them into overlapping chunks, and embeds each chunk into a multi-vector representation. Re-indexing replaces any previous index. Returns the number of files and chunks indexed.

Args: folder: Path to a local directory to index.

Search the indexed folder with ColBERT-style MaxSim late interaction.

Embeds the query into token vectors and ranks every indexed chunk by score(q, d) = sum_i max_j sim(q_i, d_j). Returns up to k results, highest score first, each with its source file, score, and a snippet.

Args: query: Natural-language or keyword query. k: Maximum number of results to return (default 5).