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

ui/src/lib/codec.ts

@@ -9,6 +9,8 @@ import { indexForLetter, letterForIndex, setAlphabet, type AlphabetEntryWire } f
 import type { PlacedTile } from './client';
 import type {
   AccountRef,
+  BlockList,
+  RobotBlockEntry,
   Banner,
   BannerCampaign,
   BestMove,
@@ -576,11 +578,15 @@ export function decodeEvent(kind: string, payload: Uint8Array): PushEvent | null
 
 // --- social encoders ---
 
-export function encodeTarget(accountId: string): Uint8Array {
+export function encodeTarget(accountId: string, gameId?: string): Uint8Array {
   const b = new Builder(64);
   const id = b.createString(accountId);
+  // game_id is set only by an in-game block, so a disguised-robot opponent is recorded
+  // per-game; every other target path omits it.
+  const gid = gameId ? b.createString(gameId) : 0;
   fb.TargetRequest.startTargetRequest(b);
   fb.TargetRequest.addAccountId(b, id);
+  if (gid) fb.TargetRequest.addGameId(b, gid);
   return finish(b, fb.TargetRequest.endTargetRequest(b));
 }
 
@@ -722,14 +728,25 @@ export function decodeOutgoingList(buf: Uint8Array): AccountRef[] {
   return out;
 }
 
-export function decodeBlockList(buf: Uint8Array): AccountRef[] {
+export function decodeBlockList(buf: Uint8Array): BlockList {
   const l = fb.BlockList.getRootAsBlockList(new ByteBuffer(buf));
-  const out: AccountRef[] = [];
+  const blocked: AccountRef[] = [];
   for (let i = 0; i < l.blockedLength(); i++) {
     const r = l.blocked(i);
-    if (r) out.push(decodeAccountRef(r));
+    if (r) blocked.push(decodeAccountRef(r));
   }
-  return out;
+  const robots: RobotBlockEntry[] = [];
+  for (let i = 0; i < l.robotsLength(); i++) {
+    const r = l.robots(i);
+    if (r)
+      robots.push({
+        id: r.id() ?? '',
+        displayName: r.displayName() ?? '',
+        gameId: r.gameId() ?? '',
+        seat: r.seat(),
+      });
+  }
+  return { blocked, robots };
 }
 
 export function decodeFriendCode(buf: Uint8Array): FriendCode {