feat(ui): batch of UI polish tweaks

- admin dashboard "Users" count excludes robots (CountUsers, humans only)
- lobby finished-game delete reveal: background matches header/tab-bar (--bg-elev)
- mobile: swipe up on the zoom-out board (no staged tiles) shuffles the rack
- lobby: status icons -25%, game-row top/bottom padding halved
- toast: info tier drifts up ~a tab-bar height while fading over 2s and dismisses
  on tap; error tier unchanged
- game: confirm-move button stays pinned at the right edge; rack tiles shrink to
  fit so a full rack never overflows onto it
- telegram: a successful invite-link redeem shows a welcome window pointing at the bot
- settings: remove the grid-lines toggle; the board is always a gapless checkerboard
- settings/comms hubs: the selected tab highlight wraps icon + label as a pill

Docs: UI_DESIGN (toast, board surface, selected tab), PLAN; e2e updated for the
removed grid-lines toggle.

docs/UI_DESIGN.md

@@ -172,11 +172,9 @@ except Login uses `Screen`.
 - **Bonus-square labels** — a Settings choice (`boardlabels.ts`): `beginner` shows a
   split `3×` / `word` (localized слово/буква), `classic` a single `3W` / `3С`, `none`
   nothing. Default **beginner**.
-- **Grid lines** — a Settings toggle, **default off**. Off: a **gapless
-  checkerboard** — plain cells alternate two shades, and tiles get rounded corners with a
-  soft right-side shadow so adjacent gapless tiles still read apart, reclaiming ~14px of
-  board width. On: the classic lined grid, where the inter-cell gap shows a contrasting
-  `--cell-line` (darker in light, lighter in dark) to avoid a wavy-line optical illusion.
+- **Board surface** — always a **gapless checkerboard** (there is no grid-lines setting):
+  plain cells alternate two shades, and tiles get rounded corners with a soft right-side
+  shadow so adjacent gapless tiles still read apart, reclaiming ~14px of board width.
 
 ## Controls
 
@@ -242,7 +240,9 @@ game **becomes your turn or finishes** while the lobby is open, that status emoj
 twice** (a two-cycle opacity fade, ~2 s; suppressed under reduce-motion) to draw the eye — the
 opponent's-turn change is silent. Each card's blink is keyed by game id, so overlapping
 events animate in isolation, and the newest bottom toast cancels the previous one and replays
-its entrance (`components/Toast.svelte`, re-keyed on a per-message sequence).
+its entrance (`components/Toast.svelte`, re-keyed on a per-message sequence). An **info** toast
+lives ~2 s, drifting up by about the tab-bar height as it fades (a plain fade, no travel, under
+reduce-motion); an **error** toast dwells longer (~4 s). Either dismisses instantly on tap.
 
 **Simultaneous-game cap.** When the player is at the active-quick-game cap (`games.list`
 `at_game_limit`), the lobby's **New Game** tab is **disabled** (greyed via the shared
@@ -255,8 +255,11 @@ enabled on the first, uncached load) and flip in place when an event refreshes t
 
 - **Settings hub** (`screens/SettingsHub.svelte`, the lobby ⚙️ tab): one nav bar + a bottom
   tab bar over four bodies — ⚙️ Settings, 👤 Profile, 🤝 Friends, ℹ️ About — switched in
-  place; back always returns to the lobby. Guests see all but Friends. The lobby ⚙️ badge and
-  the 🤝 tab badge both show the pending incoming-friend-request count.
+  place; back always returns to the lobby. The **selected** tab is marked by a filled pill
+  hugging its icon **and** label (with an accent underline) — a persistent selection cue that
+  the plain, unhighlighted action tabs (lobby nav, in-game controls) never carry. Guests see
+  all but Friends. The lobby ⚙️ badge and the 🤝 tab badge both show the pending
+  incoming-friend-request count.
 - **Friends** (`screens/Friends.svelte`, the Settings hub's 🤝 tab): an "add a friend" block
   pairing a code **input** with a **Show my code** action that reveals a large 6-digit
   code + its expiry; then the incoming **requests** (Accept / Decline), the **friends**