fix(social): robot blocks

Blocking an auto-match opponent who is secretly a pooled robot is recorded  instead in a separate `robot_blocks` table.

Now blocking behaves the same in that game (struck name, hidden composer) and lists the blocked opponent under the name you saw, but is recorded only against that game — the disguise holds, the shared robot is never globally blocked, and the matchmaker keeps pairing you with robots (so you can never block yourself out of opponents).

- the shared robot account is never put in `blocks`
- the matchmaker keeps it free and it is not blocked under its other per-game names
- the blocked list and the in-game card still show it by joining that table; an unblock deletes the row

pkg/fbs/scrabble.fbs

@@ -504,9 +504,12 @@ table StatsView {
 }
 
 // TargetRequest names a single counterpart account (friend request/cancel/unfriend,
-// block/unblock).
+// block/unblock). game_id is set only by an in-game block of a disguised-robot opponent,
+// so the backend can record the per-game robot block (the seat name the player saw)
+// against that game; every other path leaves it empty (FlatBuffers-optional).
 table TargetRequest {
   account_id:string;
+  game_id:string;
 }
 
 // FriendRespondRequest accepts or declines a pending request from a requester.
@@ -548,9 +551,22 @@ table RedeemResult {
   friend:AccountRef;
 }
 
-// BlockList is the accounts the caller has blocked.
+// RobotBlockRef is one blocked disguised-robot opponent: a per-game record (not a real
+// account) carrying the game name the player saw and the game/seat it was blocked in, so
+// the blocked list shows it as a distinct personality and the in-game card can re-mark
+// that seat. Its id is the robot_blocks row, used to unblock it.
+table RobotBlockRef {
+  id:string;
+  display_name:string;
+  game_id:string;
+  seat:int;
+}
+
+// BlockList is the accounts the caller has blocked, plus the per-game disguised-robot
+// blocks (robots) which are not real accounts.
 table BlockList {
   blocked:[AccountRef];
+  robots:[RobotBlockRef];
 }
 
 // InvitationInvitee is one invitee's seat and response, name resolved.