feat(events): add uniform root-state reset

[TATP-233]

Closes #1074
Umbrella: #1042

Summary

• port pinned mjlab 1.6.0 reset_root_state_uniform to the NumPy manager MDP surface;
• sample pose/velocity offsets from env.rng, preserve default_quat * delta_quat, and apply env.scene.env_origins;
• stage one 13-D world-frame root state through the existing entity/reset transaction;
• fail closed for invalid ranges and for fixed-base/mocap entities without a formal root-write contract;
• cover seeded/partial/all-env sampling, single-env shape, non-zero origins, quaternion/velocity semantics, rollback, and exactly-once transaction composition.

Boundaries

• no production task or Hydra owner migration;
• no new backend, lifecycle, runner, IPC, or script contract;
• no joint-reset, terrain, push, mocap, or legacy fallback path;
• reset hot paths use cached entity/root layout state only.

Validation

• uv run pytest -q tests/envs/mdp/test_events.py tests/base/test_reset_state.py tests/base/test_entity_facade.py tests/envs/test_manager_based_rl_env.py — 77 passed;
• uv run pytest -q tests/envs/mdp tests/managers/test_event_command_metrics_recorder.py tests/managers/test_core_managers.py — 78 passed;
• make type — mypy and pyright passed;
• make test-all — ruff/mypy/pyright passed; 1958 passed, 26 skipped, 275 deselected, 1 xfailed; benchmark smoke 32/33 module and 33/34 script, with only platform-optional MLX skipped.

Change accounting

• source-derived behavior/signature: 29 added lines;
• mechanical Torch→NumPy conversion: 21 added lines;
• UniLab-specific glue and focused tests: 331 added lines (including the 300-line focused test module), within the declared 350-line budget;
• modified existing: 2 files, +81/-2;
• new: 1 test file, +300;
• deleted: 0 files, 2 replaced LOC;
• total: 3 files, +381/-2.