feat(logging): add W&B worker GPU system metrics

[EazyReal]

Description

In single-controller training, the controller owns the primary W&B run while actor/rollout/critic workers own the CUDA devices. Controller-only W&B logging can miss worker GPU utilization. This PR adds opt-in worker-side W&B shared-mode clients for system metrics.

Key behavior:

• Disabled by default under stats_logger.wandb.system_metrics.enabled.
• Requires stats_logger.wandb.mode: shared; existing disabled, offline, and online runs keep current behavior.
• Worker clients attach to the same run as non-primary clients, labeled by role/rank, with x_update_finish_state=False so workers cannot finalize the primary run.
• roles defaults to train/rollout roles; roles: null enables every non-service worker role while skipping *-data and *-guard service workers.
• Worker init/finish is idempotent, lock-protected, and warning-only on W&B worker init failures.
• English/Chinese docs and generated CLI references cover the config.

stats_logger:
  wandb:
    mode: shared
    system_metrics:
      enabled: true
      roles: [actor, rollout]
      gpu_device_ids: null

Validation

• uv run pytest -q tests/test_wandb_system_metrics.py
• uv run ruff check areal/api/cli_args.py areal/utils/wandb_system_metrics.py docs/generate_cli_docs.py tests/test_wandb_system_metrics.py
• uv run ruff format --check areal/api/cli_args.py areal/utils/wandb_system_metrics.py docs/generate_cli_docs.py tests/test_wandb_system_metrics.py
• uv run python docs/generate_cli_docs.py
• git diff --check

Related Issue

Supersedes detached-fork #1338.

Type of Change

• New feature
• Documentation update
• Test coverage improvement

[gemini-code-assist]

Code Review

This pull request introduces worker-side Weights & Biases (W&B) system metrics collection, allowing GPU worker processes to attach to the same shared W&B run as the controller. It adds a new WandBSystemMetricsConfig configuration, integrates initialization and cleanup hooks across RPC servers and schedulers, and adjusts trainer initialization order to ensure the controller's primary run is established first. Feedback on the changes suggests resolving a type mismatch in WandBSystemMetricsConfig.roles where a tuple is used as a default value for a list-annotated field, recommending the use of default_factory instead.

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[EazyReal]

@garrett4wade @nuzant @sitabulaixizawaluduo @rchardx @fishcrap @HwVanICI @guozhihao-224 Could I get a quick review on this W&B metrics PR? It adds worker GPU system metrics without changing training behavior.

[EazyReal]

@garrett4wade if you have bandwidth, would appreciate a review on the W&B worker metrics config.