docs(ui): finalize docs sync — README finalized-web summary + topic links (F7)

The de-archaeology and the ui/docs index landed in the earlier reorg
(0 "Phase N" refs in ui/docs/; 24 topic docs linked). This finishes the
sync: ui/README.md gains a finalized-web-target summary and links the new
topic docs (design-system, a11y, error-state-ux, pwa-strategy).
docs/ARCHITECTURE.md and docs/FUNCTIONAL.md need no change — they cover
the backend/gateway/cross-service contracts with no stale UI statements;
the finalized UI is client-local UX documented under ui/docs/. Marks F7
done.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/README.md

@@ -11,6 +11,11 @@ directly in Wails on desktop. All network I/O lives on the
 TypeScript side via ConnectRPC, so the Go module is a pure compute
 boundary on every platform.
 
+The web target is a finalized, installable PWA: a shared design-token
+system with light/dark themes, WCAG 2.2 AA accessibility, en/ru
+localisation with a persisted choice, a central error surface, and
+offline tolerance — see the topic docs below.
+
 The legacy Fyne client under `client/` is reference-only.
 Nothing in `ui/` imports from it.
 
@@ -98,6 +103,15 @@ Linked topic docs:
   order draft store, persistence, history-mode wiring.
 - [`docs/wasm-toolchain.md`](docs/wasm-toolchain.md) — TinyGo build,
   loading recipe, bundle size budget.
+- [`docs/design-system.md`](docs/design-system.md) — design tokens,
+  light/dark theming, component conventions.
+- [`docs/a11y.md`](docs/a11y.md) — WCAG 2.2 AA approach, axe + keyboard
+  gates, shared a11y primitives.
+- [`docs/error-state-ux.md`](docs/error-state-ux.md) — central error
+  surface, shared loading/empty/error states, selection marker, sheet
+  dismissal.
+- [`docs/pwa-strategy.md`](docs/pwa-strategy.md) — installable, offline
+  PWA: service worker, manifest, icons.
 - [`docs/testing.md`](docs/testing.md) — Tier 1 per-PR + Tier 2
   release test tiers.