[InventivetalentDev]

Scene documents and the editor previously selected one entity animation even though the renderer supports weighted clips. Entities can now store a nonempty animation.clips list with names and optional weights, while existing animation.name documents keep working.

The editor adds clip selection, removal, sliders, and numeric weights. Weight changes preserve the shared playback clock; clip changes also preserve the live clock when asynchronous loading finishes. Pause, speed, loop, seeking, and restart apply to the blend. JSON saves and copied embeds capture the live time, and off-screen embeds restore the blend after recreating their renderer.

Weights default to 1, must be finite and nonnegative, and are not normalized. Clip names must be unique and must be the entity's own animations: names inherited from Object.prototype, such as constructor, are missing clips. The loader resolves every clip before starting a blend, and a missing clip rejects and disposes the staged document. The HTTP API also limits a blend to 32 clips and each weight to 1024. Reference and editor documentation describe the format and controls.

Validation:

• yarn test: 804 passed. Scene and codec tests cover old and blended documents, validation including duplicate and inherited clip names, additive weights, repeated draws and layers, shared time and pause, and atomic load failure.
• yarn test:package (11), yarn test:api (18, including the clip-count and weight limits), yarn test:embed (15) and yarn test:node (6) pass.
• Library build, root typecheck, editor typecheck, web production build, and embed build pass.