Stage 7 polish: docs + mark Stage 7 done (Part H)

- new docs/UI_DESIGN.md (design system: shell, nav, tab-bar, tiles, board zoom/labels, HoldConfirm, banner rotator, result iconography)
- ARCHITECTURE: app-shell + announcement channel (mock->server) + hint place-on-board / no_hint_available contract + board-style setting
- FUNCTIONAL(+ru): hint-on-board, word-check constraints/throttle, board style
- PLAN: Stage 7 -> done + polish refinement note; CLAUDE sources list

PLAN.md

@@ -40,7 +40,7 @@ independent (see ARCHITECTURE §9.1).
 | 4 | Lobby & social (matchmaking, friends, block, chat, profile, nudge) | **done** |
 | 5 | Robot opponent | **done** |
 | 6 | Gateway edge (Connect/FB, platform auth, sessions, push bridge, admin) | **done** |
-| 7 | UI — playable slice (Svelte+Vite, board, lobby, chat, hint/word-check, i18n) | todo |
+| 7 | UI — playable slice + UX polish (Svelte+Vite, board, lobby, chat, hint/word-check, i18n) | **done** |
 | 8 | UI — social/account/history (friends, blocks, invitations, profile edit, stats, history/GCG) | todo |
 | 9 | Telegram integration (bot side-service, deep-link, push) | todo |
 | 10 | Admin & dictionary ops (complaint review, version reload) | todo |
@@ -525,6 +525,16 @@ Open details: deployment target/host; dashboards; load expectations.
     **bundle-size budget** — prod is ~67 KB gzip JS — and a chromium e2e). The Go
     workflows already cover the new backend/gateway/pkg code; a `game.ListForAccount`
     integration test and gateway transcode tests for the new ops were added.
+  - **UX polish** (follow-up PR): a mobile-app **app shell** (growing nav bar, content
+    pinned to the bottom) + a one-line **announcement banner** (client-side mock
+    rotation now; server-driven channel later — §10); a mobile-OS **tab bar** and a
+    reusable **HoldConfirm** press-and-hold control (MakeMove 🏁 + game-action confirms);
+    board **zoom reworked** to a fixed viewport with counter-scaled labels, corner-letter
+    tiles, contrasting grid lines, and a Settings **bonus-label style** (beginner/
+    classic/none); **hint lays its tiles on the board** (no spend when no move — a new
+    `no_hint_available` result code); the history opens as an in-place **slide-down**
+    (not a modal); word-check is alphabet/length-limited, cached and throttled. Design
+    details live in the new [`docs/UI_DESIGN.md`](docs/UI_DESIGN.md).
 
 ## Deferred TODOs (cross-stage)