Apply one operation to a project's composition

Author a scene shot and place it on a dedicated overlay track. The host validates the scene, generates and registers an immutable wrapper component source, and emits the ordinary track/clip operations carrying props.componentRef — you edit a scene SPEC, never wrapper TSX or a source hash. Registration and the composition update are ONE undoable edit; a failure publishes nothing and leaves no clip pointing at an unresolved source. Pass EXACTLY ONE of trackId (an existing dedicated scene track) or newTrack: true (mint one). That track holds scene-shot clips and gaps only — no generic component/primitive/media clips in v1 — and existing generic overlay tracks are unaffected. Scene clips use front zPlane and full-frame placement: outer per-clip region, position, scale, rotation, fit, effects, animate, params.transition, params.sequenceGroup and internal fadeIn/fadeOut are REFUSED with a path, because the shot's own layer transforms are the single transform owner. TEXT: space: "screen" text is composed above the world result, stays fixed in the frame and stays sharp through focus; space: "world" text is rasterized into the 3D scene, moves with the camera and is occluded by geometry. Screenshots and world text are UNLIT and colour-managed so product UI colours are not tinted by the studio lighting, while device bodies are lit and cast shadows; an unlit surface still occludes. SCOPE GAP (pre-existing, neither closed nor changed by scene shots): global wrap effects — composition-level grades and camera effects — do not reach front-overlay clips, so they do not affect a scene shot. Author the look INSIDE the shot (post.grain, post.vignette, post.focus, backdrop, environment) instead. DISCOVERY: there is no built-in scene primitive to look up in list_catalog; the wrapper this operation registers appears afterwards as an ordinary INSTALLED component under the existing catalog rules. ASSETS: assets binds each slot name a layer references to a media id in the same project, and the slot's declared KIND decides what it admits — an image slot takes PNG, JPEG or WebP, a video slot MP4 or WebM. Binding the wrong kind is refused with the slot's path.