refactor: enforce single critic observation contract

[TATP-233]

Summary

• replace the mixed obs/privileged/critic runtime semantics with a strict obs + optional critic contract
• update env owner layers, IPC storage, APPO and off-policy runners/learners, and Sharpa config naming to use the single critic contract
• rewrite ADR-0005 and refresh tests to lock the new contract in place

Validation

• uv run python -m compileall src/unilab
• uv run ruff check src/unilab/base/np_env.py src/unilab/utils/obs_utils.py src/unilab/utils/final_observation.py src/unilab/utils/device_utils.py src/unilab/utils/rsl_rl_vec_env_wrapper.py src/unilab/ipc/replay_buffer.py src/unilab/ipc/shared_onpolicy_storage.py src/unilab/algos/torch/appo/worker.py src/unilab/algos/torch/appo/runner.py src/unilab/algos/torch/appo/learner.py src/unilab/algos/torch/offpolicy/worker.py src/unilab/algos/torch/offpolicy/runner.py src/unilab/algos/torch/fast_sac/learner.py src/unilab/algos/torch/flash_sac/learner.py src/unilab/algos/torch/fast_td3/learner.py src/unilab/envs/locomotion/go1/joystick.py src/unilab/envs/locomotion/go2/joystick.py src/unilab/envs/locomotion/g1/joystick.py src/unilab/envs/locomotion/g1/joystick_sac.py src/unilab/envs/motion_tracking/g1/tracking.py src/unilab/envs/manipulation/sharpa_inhand/base.py src/unilab/envs/manipulation/sharpa_inhand/rotation.py scripts/train_appo.py scripts/train_offpolicy.py tests/utils/test_obs_utils.py tests/utils/test_final_observation.py tests/ipc/test_shared_onpolicy_storage.py tests/algos/test_appo_worker.py tests/algos/test_flash_sac_learner.py tests/base/test_np_env.py tests/envs/test_env_configs.py tests/scripts/test_train_scripts.py
• uv run pytest tests/utils/test_obs_utils.py tests/utils/test_final_observation.py tests/ipc/test_shared_onpolicy_storage.py tests/ipc/test_replay_buffer.py tests/algos/test_appo_worker.py tests/algos/test_flash_sac_learner.py tests/base/test_np_env.py tests/envs/test_env_configs.py tests/scripts/test_train_scripts.py -q -k "not slow and not veryslow"
• uv run pytest -m "slow or veryslow"