fix: pool-stashed transformer swap + MPS-safe vram + corrected model-zoo anchor

fix(realesrgan): switch repo from xinntao/Real-ESRGAN to lllyasviel/Annotators

refactor(tooltips): rename copy.py → tooltips.py to avoid stdlib shadow

docs: amend spec + plan with param tooltips and coming-soon model placeholders

docs: implementation plan for z-image-studio (19 tasks)