Add dataset repair core and boundary export

[Shiki42]

Summary

• add a new roboclaw.data.repair domain for dataset diagnosis, repair core, and boundary frame export
• extract shared dataset root resolution into roboclaw.data.paths and reuse it from existing dataset modules
• add focused tests for damage classification ordering, core repair flows, and boundary export behavior

Validation

• python3 -m pytest -q tests/test_dataset_repair_diagnosis.py tests/test_dataset_repair_core.py tests/test_dataset_boundary_export.py
• uvx ruff check roboclaw/data/paths.py roboclaw/data/repair tests/test_dataset_repair_diagnosis.py tests/test_dataset_repair_core.py tests/test_dataset_boundary_export.py