feat: Implement multi-round dispute lifecycle with arbitration scoring and related tests

Refactor evidence building and improve code readability in iso_adapter.py

refactor: build grading on OpenEnv Rubric system

fix: squash inflated evidence scores for wrongly contested concedable cases

feat: harden grader to penalise shallow operational behaviour

feat: make note grading contextual per-case harmful evidence

feat: harden grading, expand task catalog, add episode persistence

refactor: reorganize source files into core/, evaluation/, runners/, scenarios/ directories