feat(config): support registry config factories

[TATP-233]

Summary

• make zero-argument EnvCfg factories the formal registry config-owner contract while retaining class decorators as the same callable shape
• materialize and type-check configs through one cold path used by env construction and Hydra reward-target resolution
• remove the visualization entrypoint's dependency on private config-class registry state

Scope

• no Go2 production registration, Hydra path migration, backend, lifecycle, runner, or IPC changes
• 4 modified files; 123 UniLab-specific lines added and 27 existing lines removed
• 0 source-derived lines, 0 mechanical NumPy-conversion lines, 0 files added/deleted
• contract follows ADR-0006's task-owned plain config factory decision and remains compatible with ADR-0004 bootstrap

Validation

• focused registry/config/visualization: 43 passed
• make test-all: 2009 passed, 27 skipped, 276 deselected, 1 xfailed
• ruff, mypy, and pyright passed
• benchmark smoke passed in module and script modes; each had one platform-optional MLX skip
• remote CI/Docs intentionally skipped under the Roadmap: 将 UniLab 迁移为社区通用的 Manager-Based API #1042 child-PR strategy

Closes #1090
Umbrella: #1042