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.

PLAN.md

@@ -1258,6 +1258,17 @@ cannot submit; three-way admin filter.
     first + surname initial / first + full surname), composed deterministically per pool slot (stable
     across restarts). `Pick(variant)` is variant-aware: a Russian game draws Russian names with ≤ ~20%
     Latin, an English game the Latin pool. Robot identities are keyed `robot-<lang>-<index>`.
+  - **Robot names — per-game variety** (post-release, 2026-06): the seeded pools above now only back
+    each account's *fallback* name. The disguised reaper stamps a **fresh per-game name** on the robot's
+    seat — a new `game_players.display_name` snapshot, which also captures humans' names so a later rename
+    no longer rewrites past games (a reader falls back to the account name for a pre-migration row). The
+    name is drawn 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 (stem + optional `.`/`_` + optional trailing number). Routing keeps the spirit of `Pick`
+    (Russian: Cyrillic + ≤20% Latin, never a CJK script; English: the full corpus) via `robot.PickNamed`.
+    `account.ValidateDisplayName` was loosened to admit a **trailing run of ≤5 digits** (mirrored in
+    `ui/src/lib/profileValidation.ts`), so "Player2007"-style handles are valid for humans too and the
+    disguised robot stays indistinguishable.
   - **Robot timing** (#4, interview): the fixed `2 + 88·u^3.5` move delay became move-number-aware — the
     band interpolates from [3,10] min at the first move (raised from [1,5] in round 4, #14) to [10,90] min
     by ~28 moves, right-skewed by k=4, so early moves are quick and the endgame can be long. A daytime