Fix CI validation workflow: Add strict None checks for Mypy compliance

Fix final OpenEnv validator compliance: inference stdout format, Dockerfile deps, API vars, and grader bounds

Fix reward calculation logic in SupportTicketEnv to ensure proper accumulation across steps and resolve test failures.

fix: lint/type issues and ensure mypy/ruff pass

chore: prepare Round-1 OpenEnv submission (validator, evaluator, tests, CI, docs)