Add production Task lifecycle check command

[ChinmayK0607]

Why

Authors need a fast way to catch environment startup, Task setup, and grader integration failures before paying for a full rollout. hud check --start-only stops after a cheap smoke test, and direct-answer mode exercises the grader without model inference. Agent mode remains available when full behavior is required.

What changed

• add hud check <task> with explicit start-only, direct-answer, and agent proof strategies
• support local sources, attached environments, HUD runtimes, and hosted execution
• report environment startup, Task startup, agent execution, grader execution, and reward separately
• emit a stable hud.task-check.v1 JSON contract and actionable exit codes
• redact and bound evidence, attribute lifecycle failures, and clean up unfinished direct sessions
• share Task resolution and placement logic with the existing hud task commands

Dependency

Stacked on #530 because hosted checks use its control-channel stability and connection-phase attribution.

Test plan

• uv run --extra dev pytest hud/cli/tests/test_check.py -q (25 passed)
• Ruff
• Pyright
• local Task lifecycle and attached-environment integration coverage

Made with Cursor

Submitted unintentionally; withdrawing this review.

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