feat(robot): per-game display names from a wide name corpus

Decouple the displayed opponent name from the small pool of durable robot
accounts: the disguised auto-match robot now gets a freshly composed name each
game, stamped on a new game_players.display_name seat snapshot. The snapshot
also captures humans' names, freezing what an opponent sees for the life of a
game (a later rename no longer rewrites past games); readers fall back to the
account's current name for pre-migration rows.

Names come from a wide composed corpus (internal/robot/namevariety.go): Western
locales (EN/DE/ES/IT/FR/PT), native Japanese/Chinese names, a gender-agreed
Russian pool, and human-style handles. Routing keeps Pick's spirit -- a Russian
game draws Cyrillic + <=20% Latin and never a CJK script; an English game the
full corpus -- via robot.PickNamed.

Loosen account.ValidateDisplayName (and the UI mirror) to admit a trailing run
of up to five digits, so "Player2007"-style handles are valid for humans too
and the disguised robot stays indistinguishable.

Migration 00007 adds game_players.display_name (additive, NOT NULL DEFAULT '');
jet regenerated. Docs (ARCHITECTURE 7, FUNCTIONAL + _ru, PLAN, README) updated.

docs/ARCHITECTURE.md

@@ -392,13 +392,25 @@ replay. A pool of durable accounts — each a `kind='robot'` identity (§4), key
 `robot-<lang>-<index>` and provisioned at startup with **chat blocked but friend
 requests open** — a request to a robot is accepted as pending and expires unanswered
 (the robot never responds), mirroring a human who ignores it; the chat
-block backs the human-like names (there is no DM surface; chat is per-game). Names are
-**composed per language** from a first-name pool (32 full + 32 colloquial forms) and
-a surname pool (gender-agreed for Russian) in one of three forms (first only /
-first + surname initial / first + full surname), deterministically per pool slot so
-they stay stable across restarts. Substitution is **variant-aware**: a Russian game
-(Russian Scrabble or Эрудит) draws a Russian-named robot with at most ~20% Latin, an
-English game the Latin pool.
+block backs the human-like names (there is no DM surface; chat is per-game).
+
+**Per-game names.** A seated player's display name is **snapshotted on the seat**
+(`game_players.display_name`) when the seat is taken — a human's then-current name, or a
+disguised robot's freshly composed name — so the name an opponent sees is frozen for the life
+of the game (a later rename never rewrites past games) and a small pool of accounts presents
+as an ever-changing crowd. A reader falls back to the account's current name when a seat
+carries no snapshot (a pre-migration row). Each durable robot account still seeds a stable
+fallback name (32 composed per language), but the disguised reaper stamps a **fresh per-game
+name** drawn from a wide composed corpus: Western first/surname pools per locale (English,
+German, Spanish, Italian, French, Portuguese) in one of three forms (first only / first +
+surname initial / first + full surname), native Japanese/Chinese names, a gender-agreed
+Russian pool, and human-style handles (a stem, an optional `.`/`_`, an optional trailing
+number). Selection is **variant-aware**: a Russian game (Russian Scrabble or Эрудит) draws a
+Cyrillic name or handle with at most ~20% Latin analogue and **never a CJK script**; an
+English game draws the full international corpus. Every composed name stays within the
+editable display-name format (`account.ValidateDisplayName`) — which now admits a **trailing
+run of up to five digits** (so "Player2007"-style handles are valid for humans too) — so the
+disguised robot stays indistinguishable from a person.
 
 - **Balance**: at game start it decides once whether to play to win, with
   `P(play-to-win) ≈ 0.40` (so the human wins ≈ 60%), derived from the seed.

docs/FUNCTIONAL.md

@@ -146,8 +146,10 @@ yet holds to the plan once the bag empties, and plays at a human pace — short
 times for most moves, the occasional long one, and a night-time pause that tracks the
 player's own day. It answers a nudge
 within a few minutes and nudges back when the player has been away a long time. It
-carries a human-like, language-appropriate name (a Russian game draws mostly Russian
-names); it does not chat, and **silently ignores friend requests** — a request to a
+carries a human-like, language-appropriate name — a fresh one each game, drawn from a wide
+international pool of real names and handles, so the arena feels populated by many different
+players (a Russian game shows mostly Russian names, never East-Asian scripts; an international
+game the full mix); it does not chat, and **silently ignores friend requests** — a request to a
 robot stays pending and expires, exactly like a human who never responds.
 
 The same robot also backs the **honest-AI quick game** the player chooses directly (above). There
@@ -182,8 +184,9 @@ message raises an **unread badge** on the game's score bar and the 💬 until th
 
 ### Profile & settings
 Edit the display name (letters joined by a single space / "." / "_" separator, with an
-optional trailing ".", up to 32 characters and at most 5 special characters — the "." / "_"
-punctuation, spaces aside), the timezone (chosen as a UTC offset), the
+optional trailing "." or a trailing run of up to five digits, up to 32 characters and at most
+5 special characters — the "." / "_" punctuation, spaces and digits aside), the timezone
+(chosen as a UTC offset), the
 daily away window (on a 10-minute grid, at most 12 hours, wrapping midnight) and the
 block toggles. The profile form is edited inline (no separate edit mode). Linking
 an email or Telegram and merging accounts are covered under "Accounts, linking &

docs/FUNCTIONAL_ru.md

@@ -151,7 +151,9 @@ nudge) приходят от бота **этой партии** — по язы
 человеческим темпом — чаще короткие раздумья, изредка долгие, и ночная пауза,
 подстроенная под день игрока. На nudge отвечает за несколько минут и
 сам шлёт nudge, когда игрок надолго пропал. Носит человекоподобное имя, подходящее
-языку партии (в русской партии — в основном русские имена); не общается в чате и
+языку партии — каждую партию новое, из широкого международного пула реальных имён и
+никнеймов, так что арена кажется полной разных игроков (в русской партии — в основном
+русские имена, без восточноазиатских письменностей; в международной — весь спектр); не общается в чате и
 **молча игнорирует заявки в друзья** — заявка роботу остаётся в ожидании и истекает,
 ровно как у человека, который не отвечает.
 
@@ -186,8 +188,8 @@ push доставляется через платформу.
 
 ### Профиль и настройки
 Редактирование отображаемого имени (буквы, разделённые одиночным пробелом / «.» /
-«_», с необязательной завершающей «.», до 32 символов и не более 5 спецсимволов —
-пунктуации «.» / «_», пробелы не в счёт), таймзоны (выбор смещения от
+«_», с необязательной завершающей «.» или хвостом до пяти цифр, до 32 символов и не
+более 5 спецсимволов — пунктуации «.» / «_», пробелы и цифры не в счёт), таймзоны (выбор смещения от
 UTC), суточного окна отсутствия (away; сетка по 10 минут, не более 12 часов, с
 переходом через полночь) и переключателей блокировок. Форма профиля редактируется
 сразу (без отдельного режима редактирования). Привязка email и Telegram, а также