Add verified three-cup annotations and mixed-schema loader documentation

Organize archives by task and consolidate shared metadata

Add verified four-task release: README.md

Add verified four-task release: release_manifest.json

Add verified four-task release: metadata/user_repairs_20260910_promotion.json

Add verified four-task release: metadata/stack_two_cubes.files.jsonl

Add verified four-task release: metadata/put_mug_on_coaster.files.jsonl

Add verified four-task release: metadata/put_cup_in_bowl.files.jsonl

Add verified four-task release: metadata/put_bowl_on_rack.files.jsonl

Add verified four-task release: metadata/build_progress.json

Add verified four-task release: metadata/USER_REPAIRS_20260910.md

Add verified four-task release: episodes.jsonl

Add verified four-task release: SHA256SUMS

Add verified four-task release: stack_two_cubes.tar

Add verified four-task release: put_mug_on_coaster.tar

Add verified four-task release: put_cup_in_bowl.tar

Add verified four-task release: put_bowl_on_rack.tar

initial commit