feat(logging): configure W&B identity and synchronize run ownership

[shuangwu]

Summary

Expose W&B run identity through typed logging configuration and fix cached run
ownership when applications initialize, finish, or replace the active SDK run.

• Add logging.wandb_run_id, wandb_run_name, and wandb_resume; preserve
  timestamp-based defaults, existing project/group fields, and vision config behavior.
• Adopt and return an already-active SDK run without reconfiguring it.
• Clear stale handles on failed initialization and when the active run is
  finished/replaced; require explicit initialization to adopt a replacement.
• Handle the absent optional SDK without an undefined-global failure.
• Document ownership, defaults, and the single-active-run limitation.

This replaces the need for an application to intercept wandb.init to supply
launcher-derived identity. No launcher-specific environment parsing, report
filtering, or application-specific naming policy is added.

Validation

28 tests pass (test_wandb_identity.py and test_logging_level.py), covering
default/explicit identity, resume modes, invalid settings, repeated/external
initialization, failed initialization, finished/replaced runs, missing SDK,
and unchanged vision-generation identity. Tests use a fake SDK and make no
remote W&B calls. Ruff and git diff --check pass.

Independent of pending #747: based directly on upstream main, with none of that
PR's watchdog/launcher/unregister commits included.

Initialization policy

Initialization remains best-effort, including wandb_resume="must": SDK initialization errors are logged and training continues without W&B logging. wandb_resume=None defers to SDK settings, including environment configuration; it does not guarantee that resuming is disabled. An application-owned active run retains its existing identity and policy.