chore: remove lucy-2.1-vton

[AdirAmsalem]

Summary

• Remove lucy-2.1-vton and its lucy-vton alias from the Python SDK: type literals, MODEL_ALIASES, and the realtime/video _MODELS registries. models.realtime() / models.video() now raise ModelNotFoundError for these names.
• Keep lucy-2.1-vton-2 as the supported legacy VTON2 alias (deprecation warning → lucy-vton-2), with its existing endpoint path.
• Move the virtual try-on example and the realtime playground VTON option to lucy-vton-3.
• Tests: drop the retired lucy-2.1-vton assertions only (no added tests).

Mirrors the JS SDK change in DecartAI/sdk#177.

Validation

• uv run ruff check + uv run black --check on changed files (clean)
• uv run pytest tests/test_models.py (13 passed)
• uv run pytest (64 passed, 20 skipped)

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Note

Medium Risk
Breaking change for any code still passing lucy-2.1-vton or lucy-vton; behavior is intentional model retirement, not a runtime bug in active paths.

Overview
Removes the retired virtual try-on identifiers lucy-2.1-vton and lucy-vton from the Python SDK: they are dropped from RealTimeModels / VideoModels, from MODEL_ALIASES, and from the realtime and video _MODELS registries (including job/stream paths). Callers using those names will get ModelNotFoundError instead of a resolved definition.

Keeps lucy-2.1-vton-2 as the legacy alias that warns and maps to lucy-vton-2. Docs in models.video() no longer list lucy-2.1-vton.

Updates sample tooling to the current VTON model: examples/video_tryon.py and the realtime playground model list use lucy-vton-3 instead of lucy-2.1-vton. Tests drop assertions for the removed models.

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