shader-gen

# Shader Generator Submit-only: creates a backend generation job, returns `jobId`. Use the `track_progress` tool for job lifecycle after submission. **Always use `generate.ts` for new shaders.** Manual authoring is only for editing existing asset code — never as a fallback when generation fails. ## Catalog-first rule — try existing assets before generation Before generating a shader, call `browse_library` unless the user names an exact asset id that is already visible in `read_project`. `browse_library` is the source of truth for built-in effects, built-in transitions, and project effect/transition assets. Built-ins are stable global asset ids, not per-project DB assets, so they may not appear in `read_project` asset lists. Apply catalog entries with `edit_item`, do **not** call `submit_shader`. Good catalog searches: ```text browse_library(query: "zoom") browse_library(category: "transitions", query: "dissolve") browse_library(category: "audio-fx") ``` Generate only when no catalog entry matches the user's intent closely enough. ### `builtin:zoom` is track-bound only — DO NOT use item-bound The default effect mode is `"item-bound"` (attach to a single item via `targetItemId`). **`builtin:zoom` does NOT render in item-bound mode** — the renderer reads zoom data exclusively from track-bound effect items. An item-bound zoom inserts into the DB silently but shows nothing in preview. Use `mode: "track-bound"` with `trackId` + `trackBoundFrom` + `trackBoundDurationInFr...