Combine multiple OOT modules into a single Docker image using
multi-stage COPY from existing single-OOT images. No recompilation
needed — fast and deterministic.
New MCP tools: build_multi_oot_image, list_combo_images, remove_combo_image
Also hardens _load_registry() to validate per-entry instead of
all-or-nothing, preventing one corrupt entry from discarding the
entire registry.