feat: add Go2 manager config fixture

[TATP-233]

Summary

• add an unregistered task-owned Go2 flat Manager-Based config factory
• preserve legacy 49/52 observations, 12-D position action, command/reset/reward/termination semantics, and named home defaults
• prove construction, reset, and one step on a real MuJoCo backend with finite NumPy NpEnvState outputs

Scope

• no production registry or Hydra changes
• no backend, entity, lifecycle, runner, or IPC contract changes
• 2 files, 519 lines added; 223 UniLab config lines and 296 near-risk test lines; no source-derived manager port or deletions

Validation

• make test-all: 2004 passed, 27 skipped, 276 deselected, 1 xfailed
• benchmark smoke: both modes passed with one platform-optional MLX skip each
• focused manager/MDP regression: 109 passed
• ruff, mypy, and pyright passed
• remote CI intentionally not run or awaited under the Roadmap: 将 UniLab 迁移为社区通用的 Manager-Based API #1042 child-PR strategy

Closes #1086
Umbrella: #1042