fix(game): show granted/bought hints in-game — finish the D31 wire removal

The in-game hint badge ignored the payments hint wallet: loading a game clobbered
app.profile.hintBalance with the deprecated StateView.wallet_balance (zeroed in the
D31 domain removal but left in the protocol as a dead 0, then synced over the real
balance at game load).

Finish the removal honestly. StateView carries the per-game allowance alone
(hints_remaining); the purchasable wallet lives solely on the profile and the client
adds it (lib/hints). Removed StateView.wallet_balance across every layer — backend
StateView/DTO, notify.PlayerState (live events), gateway StateResp + wire.StateView,
the client model/codec/mock/localgame — and dropped the now-unused wallet arg from
hintsRemaining. The FBS field is tombstoned `(deprecated)` (not deleted) so the vtable
slots after it stay stable across a rolling deploy; no accessor is generated. HintResult
keeps wallet_balance (the real post-spend payments balance the client adopts into the
profile). The StateView type no longer has walletBalance, so the clobber cannot return
without a compile error.

Tests: hintsRemaining (2-arg); hints.hintsLeft (allowance + live wallet, no strip); the
game state/hint integration (allowance-only HintsRemaining); gateway transcode; FBS regen.

ui/src/gen/fbs/scrabblefb/state-view.ts

@@ -69,11 +69,6 @@ alphabetLength():number {
   return offset ? this.bb!.__vector_len(this.bb_pos + offset) : 0;
 }
 
-walletBalance():number {
-  const offset = this.bb!.__offset(this.bb_pos, 16);
-  return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
-}
-
 hintUnlockLeftSeconds():number {
   const offset = this.bb!.__offset(this.bb_pos, 18);
   return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
@@ -131,10 +126,6 @@ static startAlphabetVector(builder:flatbuffers.Builder, numElems:number) {
   builder.startVector(4, numElems, 4);
 }
 
-static addWalletBalance(builder:flatbuffers.Builder, walletBalance:number) {
-  builder.addFieldInt32(6, walletBalance, 0);
-}
-
 static addHintUnlockLeftSeconds(builder:flatbuffers.Builder, hintUnlockLeftSeconds:number) {
   builder.addFieldInt32(7, hintUnlockLeftSeconds, 0);
 }
@@ -144,7 +135,7 @@ static endStateView(builder:flatbuffers.Builder):flatbuffers.Offset {
   return offset;
 }
 
-static createStateView(builder:flatbuffers.Builder, gameOffset:flatbuffers.Offset, seat:number, rackOffset:flatbuffers.Offset, bagLen:number, hintsRemaining:number, alphabetOffset:flatbuffers.Offset, walletBalance:number, hintUnlockLeftSeconds:number):flatbuffers.Offset {
+static createStateView(builder:flatbuffers.Builder, gameOffset:flatbuffers.Offset, seat:number, rackOffset:flatbuffers.Offset, bagLen:number, hintsRemaining:number, alphabetOffset:flatbuffers.Offset, hintUnlockLeftSeconds:number):flatbuffers.Offset {
   StateView.startStateView(builder);
   StateView.addGame(builder, gameOffset);
   StateView.addSeat(builder, seat);
@@ -152,7 +143,6 @@ static createStateView(builder:flatbuffers.Builder, gameOffset:flatbuffers.Offse
   StateView.addBagLen(builder, bagLen);
   StateView.addHintsRemaining(builder, hintsRemaining);
   StateView.addAlphabet(builder, alphabetOffset);
-  StateView.addWalletBalance(builder, walletBalance);
   StateView.addHintUnlockLeftSeconds(builder, hintUnlockLeftSeconds);
   return StateView.endStateView(builder);
 }