Infinite loop in split_text_into_chunks when overlap >= chunk_size

Description

MiroFish's `split_text_into_chunks` function contains an infinite loop when `overlap >= chunk_size`. The loop body sets `start = end - overlap`, which — when overlap equals chunk_size — does not advance the position, causing an infinite loop that hangs the server.

Reproduction

# split_text_into_chunks(text, chunk_size=10, overlap=10)
# start = end - overlap = end - chunk_size = start (never advances)
# Infinite loop