feat(task): support seconds-based task horizons resolved against control rate (#160)

[Adityakk9031]

Summary

Resolves #160 (and #161).

Task.max_steps was previously a fixed integer step budget set at task construction time. However, benchmark tasks defined in physical time (e.g. KitchenBench) allot per-task seconds (max_seconds). Because task factories behind string registries are zero-arg and Task is embodiment-agnostic, tasks had no way to resolve physical durations into step counts prior to pairing with an embodiment.

This PR adds support for declaring task horizons in physical seconds (Task(max_seconds=...)), which eval() resolves into integer step budgets (max_steps = math.ceil(max_seconds * control_hz)) after pairing with an embodiment.

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Key Changes

• inspect_robots.task.Task: Made max_steps: int | None = None optional and added max_seconds: float | None = None. Added __post_init__ validation enforcing mutual exclusion (exactly one of max_steps or max_seconds must be set) and positive numeric ranges. task.envelope raises ConfigError if called on an unresolved max_seconds task.
• inspect_robots.compat: Added a preflight compatibility check (control_hz_missing error issue) ensuring embodiment.info.control_hz is present and $> 0$ whenever task.max_seconds is specified.
• inspect_robots.eval: Computes max_steps = math.ceil(task.max_seconds * control_hz) at eval() time, passing the resolved integer budget to bind_task hooks and rollout().
• inspect_robots.log: Added max_seconds: float | None = None to EvalSpec for reproducible log schema persistence.
• tests/test_task_horizon.py: Added unit tests covering task horizon validation, preflight control_hz compatibility checks, fractional math.ceil resolution, and EvalLog persistence.

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Verification

• Unit Tests: Executed full test suite (pytest --cov). All 716 tests passed.
• Coverage: 100% statement and branch coverage maintained across all core modules.
• Linting & Types: Passed ruff check ., ruff format --check ., and mypy.

[Adityakk9031]

@jeqcho have a look

[Adityakk9031]

@jeqcho all check pass