Stage 3: game domain (lifecycle, journal+cache, hint, word-check, GCG, stats)

internal/game drives the engine over a single match and owns everything the
engine does not: event-sourced persistence (a games row + an append-only decoded
move journal, with the live engine.Game kept warm in a cache and rebuilt by
replay on a miss), the play/pass/exchange/resign transitions with
validate-at-submit scoring, an unlimited score/legality preview, the hint
(per-game allowance + profile wallet), the word-check tool with complaint
capture, per-player game state, history and GCG export (Poslfit dialect), and a
background turn-timeout sweeper that auto-resigns overdue turns honouring each
player's daily away window. Like Stages 1-2 it is a service/store layer with no
HTTP; the gateway surface lands in Stage 6.

Engine: additive decoded domain API (Direction, SubmitPlay/SubmitExchange/
EvaluatePlay/HintView/Hand, MoveRecord.{Dir,MainRow,MainCol}, Registry.Lookup,
ParseVariant) so internal/game never imports scrabble-solver; and a Resign fix
so the resigner keeps their score yet never wins (the other player wins a
two-player game). Timeout reuses Resign.

Persistence: migration 00002 adds games, game_players, game_moves, complaints,
account_stats and extends accounts with away_start/away_end/hint_balance; go-jet
regenerated. account gained SpendHint. Config adds BACKEND_DICT_DIR (required),
BACKEND_DICT_VERSION, BACKEND_GAME_TIMEOUT_SWEEP_INTERVAL, BACKEND_GAME_CACHE_TTL;
main loads the registry at boot (hard dependency) and starts the sweeper.

Tests: engine resign + decoded-API tests; game unit tests (GCG, away-window
boundaries, hint budget, cache, keyed mutex, payload); inttest integration
(lifecycle, replay equivalence, timeout sweep with away grace, resign stats,
hint policy, word-check/complaint, per-game-lock). Docs (PLAN, ARCHITECTURE,
FUNCTIONAL +_ru, TESTING, README) updated.

docs/FUNCTIONAL.md

@@ -28,11 +28,18 @@ a `(variant, language)` pool; after 10 s with no human, the robot substitutes.
 Friend games (2–4) are formed by friend list, internal ID, or deep-link.
 
 ### Playing a game *(Stage 3)*
-Place tiles, pass, exchange, or resign. A play is validated against the
-dictionary at submit time and scored. One hint per game reveals the best move.
-The dictionary check tool is unlimited and offers a complaint. The game ends
-when the bag empties and a player clears their rack, after 6 consecutive
-scoreless turns, or by the 24-hour move timeout (auto-resign).
+Place tiles, pass, exchange, or resign. A play is validated against the game's
+dictionary at submit time and scored; an unlimited preview reports what a
+tentative move would score and whether it is legal. The dictionary check tool is
+unlimited and offers a complaint on any result. Hints are governed per game —
+whether they are allowed and how many each player starts with — and draw on a
+personal hint wallet once the per-game allowance is spent. The game ends when the
+bag empties and a player clears their rack, after 6 consecutive scoreless turns,
+by resignation, or by the per-game move timeout (5 minutes to 24 hours, default
+24 hours): a missed turn auto-resigns, except while the player is inside their
+daily away window. A resignation or timeout gives the win to the other player and
+the leaver keeps their score (two-player games; multi-player drop-out-and-continue
+arrives with the lobby in Stage 4).
 
 ### Robot opponent *(Stage 5)*
 Indistinguishable-from-human substitute in auto-match. Decides once whether to
@@ -49,7 +56,9 @@ toggles.
 
 ### History & statistics *(Stage 3)*
 Finished games are archived in a dictionary-independent form and exportable to
-GCG. Statistics: wins, losses, max points in a game, max points for one word.
+GCG. Statistics (durable accounts only): wins, losses, draws, max points in a
+game, and max points for a single move (the best play, which already includes
+every word it formed plus the all-tiles bonus).
 
 ### Administration *(Stage 9)*
 Admin (Basic Auth at the gateway) reviews word complaints, manages dictionary