Stage 17: fix the robot-nudge frequency + per-game push language

Two owner-reported defects from a live contour game.

A. Frequency: the robot's proactive nudge fired hourly for 12h+ (a 12h idle threshold
   then the 1h cooldown, uncapped). Replaced with a lengthening, randomized schedule
   (proactiveNudgeGap): the first nudge ~60-90 min into the human's turn, each later gap
   growing toward 1-6h (uniform sample in [60min, ceil], ceil ramping 90min->6h over 12h
   of idle, measured from the previous nudge), so a long wait gets a handful of
   increasingly-spaced reminders instead of a stream.

B. Language: out-of-app push routed by the recipient's GLOBAL service_language
   (last-login-wins), so after re-logging via the RU bot an English game's nudges came
   from the RU bot. Now a game push (your_turn, game_over, nudge, match_found) carries
   the game's own language (engine.Variant.Language) on push.Event, and the gateway
   routes by it (falling back to service_language for non-game pushes). The New-Game
   variant-gating guarantees the game's bot is one the player has started, so delivery is
   never blocked.

Tests: proactiveNudgeGap unit + retimed TestRobotProactiveNudge; TestVariantLanguage;
emit your_turn/game_over language; TestNudgeRoutedByGameLanguage integration. Docs:
ARCHITECTURE (§7 nudge, §10/§13 routing), FUNCTIONAL (+ _ru), PLAN tracker.

docs/ARCHITECTURE.md

@@ -141,8 +141,10 @@ arrive from a platform rather than completing a mandatory registration).
   gate (it is a product affordance, not a trust boundary). The service language is
   **persisted** per account (`accounts.service_language`, updated on every Telegram
   login — last-login-wins) and routes the user's out-of-app push back through the right
-  bot (§10); it is distinct from `preferred_language` (the interface language) and from
-  a game's variant language. Non-Telegram logins (web / email / guest) carry the
+  bot (§10) — **except a game event, which routes by the game's own language** (its variant →
+  en/ru, Stage 17), so a game's notification always comes from the game's bot rather than the
+  recipient's latest login bot. The service language is distinct from `preferred_language` (the
+  interface language) and from a game's variant language. Non-Telegram logins (web / email / guest) carry the
   gateway's default set (`GATEWAY_DEFAULT_SUPPORTED_LANGUAGES`, all variants by default).
 - The client holds `session_id` in memory for the app session (browser/OS
   storage is optional and may be unavailable; losing it means re-login).
@@ -339,8 +341,9 @@ English game the Latin pool.
   **sleeps 00:00–07:00** anchored to the **opponent's** profile timezone with a
   per-game drift of **±3 h** (fallback UTC), so its night overlaps the human's
   rather than running anti-phase; on a daytime nudge it replies near the move's lower
-  band; it proactively nudges the human after **12 hours** idle (subject to the
-  once-per-hour chat limit).
+  band; it proactively nudges the idle human on a **lengthening, randomized schedule** — the
+  first ~60-90 min into the turn, each later reminder spaced further out toward 1-6 h — so a long
+  wait gets a handful of increasingly-spaced nudges rather than an hourly stream (Stage 17).
 - **Observability**: robot accounts accrue ordinary statistics (§9) — the
   authoritative balance metric (target ≈ 40% robot wins) — and a
   `robot_games_finished_total` OTel counter plus a per-finish log give a live view.
@@ -507,11 +510,13 @@ missed while the app was hidden. **Out-of-app platform push** (Stage 9) is a fal
 the **gateway** routes from the same firehose: for an event whose recipient has **no
 live in-app stream** it resolves the backend `/internal/push-target` (their Telegram
 `external_id`, the **service language** — the bot they last signed in through, falling
-back to the interface language — and the `notifications_in_app_only` flag) and asks the
-**Telegram connector** to deliver a localized message with a Mini App deep-link
-button — only when the recipient has a Telegram identity and has not confined
-notifications to the app, so the two channels never duplicate. The connector routes by
-that language to the matching bot and renders the message in it. The out-of-app set is
+back to the interface language — and the `notifications_in_app_only` flag). A **game** event,
+however, carries the **game's own language** on the push (Stage 17), and the gateway routes by
+that instead of the service language — so a game's notification always comes from the game's bot,
+not the recipient's latest-login bot. It then asks the **Telegram connector** to deliver a
+localized message with a Mini App deep-link button — only when the recipient has a Telegram
+identity and has not confined notifications to the app, so the two channels never duplicate. The
+connector routes by that language to the matching bot and renders the message in it. The out-of-app set is
 your-turn, game-over, nudge, match-found and the invitation / friend-request notify sub-kinds;
 the connector renders the message and skips the rest. Operator broadcasts
 (`SendToUser` / `SendToGameChannel`, §10 admin) instead pick the bot by an