feat(lobby): drop left honest-AI games from the finished list

A finished honest-AI (vs_ai) game the player left — by resigning or by
abandoning it to the 7-day inactivity timeout (end_reason 'resign'/'timeout')
— no longer appears in that player's own lobby finished list.

The new game.Service.ListForLobby filters ListForAccount for the lobby
endpoint only; the admin console and the account-merge count keep the full
set. The filter keys on the game's end reason, not on which seat left, so it
extends to any player should the robot ever resign.

docs/ARCHITECTURE.md

@@ -382,7 +382,12 @@ at once, only the human is ever on the clock, so the per-turn timeout doubles as
 game emits **no `your_turn`** (the instant reply makes it redundant; `opponent_moved`
 still advances the UI), its **GCG export labels the robot seat "AI"**, and the
 games-started / -abandoned metrics carry a **`vs_ai`** attribute so AI and human games
-chart separately (the admin `/games` list and game card also show the AI flag).
+chart separately (the admin `/games` list and game card also show the AI flag). A finished
+honest-AI game the player **left** — `end_reason` `resign` or `timeout` — is also dropped from
+that player's own *finished* lobby list by `game.Service.ListForLobby` (a lobby-only filter over
+`ListForAccount`); the admin console and the account-merge count keep the full set, and a
+normally finished AI game stays. The filter keys on the game's end reason, not on which seat
+left, so it extends to any player should the robot ever resign.
 
 The robot keeps **no per-game state**: every choice is derived deterministically
 from the game's bag `seed` (a restart-stable FNV-1a mix), so a background driver