Seat web.dev on the design council; record PWA backfill

docs/architecture/10-interaction-and-feedback.md

@@ -320,6 +320,20 @@ Datasets (⌘/Ctrl+K), or check the dataset name in your spec."_ — instead of
 must match the actual cause (NN/g #9, GOV.UK error-message). The thrown
 `DatasetNotFoundError` carries `datasetName` so the surface can name it.
 
+**Resolved — service-worker update prompt & persistent storage (web.dev seat).** The build
+uses `registerType: 'prompt'`, so a new service worker waits and never takes over a running
+session on its own — the app **must** tell the user, or "ask before updating" silently means
+"never update." `orchestration/pwa.ts` consumes `virtual:pwa-register` and surfaces
+`onNeedRefresh` as a **durable** (non-auto-dismissing) info toast with a **Reload** action
+that calls `updateSW()`; `onOfflineReady` is a transient success toast. Separately, browser
+storage is best-effort and evictable under pressure, which for a local-first workspace is data
+loss — so we request `navigator.storage.persist()` once at startup
+(`infrastructure/storage-persist`), feature-detected and silent on denial (Chromium decides
+automatically; nothing for the user to act on). _(Consulted via /council → web.dev, with the
+exact API from vite-plugin-pwa/Workbox; see `reference/principles/web-dev.md`. This bullet is
+the contract; cite it, not the source.) **Known gap:** the manifest ships no icons, so the app
+is not yet installable — a design-asset task, logged not passed._
+
 ## 6. Motion & accessibility as default
 
 Not features to add later — the baseline every surface is built on.