M15.2: web app depth (WEB-1): browser storage, Web Audio, worker renders, WebGPU viewer, PWA

- Persistence: settings, shortcuts, recent projects, imported media, saved projects and
  auto-saves live in OPFS (IndexedDB fallback) through an in-memory mirror flushed in the
  background (apps/effectcraft-web/src/store.rs, persist.rs); ConfigStore gains FileOps so
  auto-save / recovery work in the browser store; the session snapshot restores the last
  project + editor state on reload; File > Open Recent works from storage.
- Audio: Web Audio output (AudioWorklet, ScriptProcessor fallback) fed by AudioPlayback::pump
  on wasm32; A/V sync from AudioContext.currentTime; meters; unlock on first gesture.
- Background jobs: engine::offload (WorkerRequest/WorkerReply protocol, Offload trait,
  run_request); Render Queue, tracker, mask tracker, Warp Stabilizer and Roto Freeze run in Web
  Workers (a second engine instance on the shared compiled module), progress streamed back;
  cancel terminates the worker.
- GPU: WebGPU viewer frames drawn straight from the compositor's texture (gpu_display on
  wasm32 when the viewer draws plainly); async readback (Gpu::read_display_async) for pixels.
- PWA: manifest, service worker precaching the build (xtask fills list/version), icons copied
  from assets/app-icon; COOP/COEP kept from cached responses; offline reload works.
- window.effectcraft: saveToBrowser, listStored, removeStored, flush; info() reports storage,
  audio, gpu, workers.
- Tests: native store + protocol + offload (render, track, cancel) tests; smoke.mjs extended
  (GPU path, worker render responsiveness, audio gesture + playback, reload persistence,
  Open Recent, offline reload).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

ROADMAP.md

@@ -20,7 +20,7 @@ once.
 | M11 | Animation tools: audio playback, meters and waveforms, Lottie import and export (done); presets, Motion Sketch, Wiggler | In progress |
 | M12 | Performance: layer cache and parallel compositing (done), GPU compositing, disk cache, motion tracking | In progress |
 | M13+ | Puppet, paint, roto, motion tracking, a plugin API | Planned |
-| M15 | The web app (WebAssembly, WebGPU) | Done, single-threaded |
+| M15 | The web app (WebAssembly, WebGPU) | Done: browser storage, Web Audio, renders and analyses in Web Workers, offline install ([docs/web.md](docs/web.md)) |
 | M14 | Built for agents: MCP server, command-line tool, control channel; Settings, keyboard shortcut editor, auto-save and crash recovery ([docs/preferences.md](docs/preferences.md)) | Done |
 
 ## How far from full parity