Added early validation for gpt-5-mini, which only supports temperature = 1, so invalid simulation configurations fail before API calls are made.
Added fail-fast handling for unrecoverable model/integration route mismatches, so run_ai_on_chapters(on_error = "skip") no longer repeats the same backend configuration failure across every simulation unit.
Added split_book_section_by_headings() to split oversized section text files into chapter-level files using known chapter headings.
Added a model column to raw simulation outputs and updated downstream summaries to preserve model-specific results instead of collapsing across models.