- save_pools: extended with split_mode and config params; per_category
mode writes categories metadata (seed, train_ratio, test_source) for
incremental append and consistency validation
- load_pools: compatible with both old format (no split_mode) and new
format; extra metadata fields ignored during load
- build_or_load_pools: signature changed to (config, strategy, db_path);
baseline_run_id read from seed.json (not config.run_id); per_category
mode does consistency check on reload and supports incremental category
append via strategy.build_incremental
- Added _to_pool_config, _read_baseline_run_id,
_validate_per_category_consistency helpers
- Tests: TestPerCategorySaveLoad with 5 test cases covering roundtrip,
missing config error, global split_mode field, legacy format compat,
multi-type categories
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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