Reporting

Report builders return list[str] and never write files themselves:

• create_typo_generation_report()
• create_autocorrect2_report()
• create_full_pipeline_report()

The full report reuses the two stage-specific report bodies. Run-level framing belongs to build_report_document(), which can add metadata that should appear only once around the combined body.

Only the pipeline layer decides when a report is written and delegates the filesystem operation to hotstring.file_io.