Stage 11: account linking & merge (email + Telegram Login Widget)

Link an email (confirm-code) or Telegram (web Login Widget) to the current
account; if the identity already has its own account, merge the two into the
one in use (the current account is primary, except a guest initiator whose
durable counterpart wins). The merge runs in one transaction
(internal/accountmerge): stats + hint wallet summed, paid_account ORed,
identities/games/chat/complaints transferred, friends/blocks de-duplicated,
the secondary kept as a merged_into tombstone so a shared finished game's
no-cascade FKs hold; a shared active game blocks the merge.

- migration 00009: accounts.paid_account, merged_into, merged_at (+ jetgen)
- internal/link orchestrator; session.RevokeAllForAccount on merge
- connector ValidateLoginWidget RPC + loginwidget HMAC validator
- edge ops link.email.request/confirm/merge, link.telegram.confirm/merge;
  supersedes the Stage 8 email.bind.* surface (request never reveals 'taken'
  before the code is verified, so a probe cannot enumerate addresses)
- UI Profile link section + irreversible-merge dialog; Telegram web sign-in
- focused regression tests (merge core, guest inversion, active-game refusal,
  finished-shared-game kept), gateway transcode + connector + UI codec/e2e
- docs: PLAN, ARCHITECTURE 3/4/9, FUNCTIONAL(+ru), module READMEs

ui/src/lib/codec.ts

@@ -19,6 +19,7 @@ import type {
   Invitation,
   InvitationInvitee,
   InvitationSettings,
+  LinkResult,
   MatchResult,
   MoveRecord,
   MoveResult,
@@ -457,22 +458,47 @@ export function encodeUpdateProfile(p: ProfileUpdate): Uint8Array {
   return finish(b, fb.UpdateProfileRequest.endUpdateProfileRequest(b));
 }
 
-export function encodeEmailBind(email: string): Uint8Array {
+// --- account linking & merge (Stage 11) ---
+
+export function encodeLinkEmailRequest(email: string): Uint8Array {
   const b = new Builder(128);
   const e = b.createString(email);
-  fb.EmailBindRequest.startEmailBindRequest(b);
-  fb.EmailBindRequest.addEmail(b, e);
-  return finish(b, fb.EmailBindRequest.endEmailBindRequest(b));
+  fb.LinkEmailRequest.startLinkEmailRequest(b);
+  fb.LinkEmailRequest.addEmail(b, e);
+  return finish(b, fb.LinkEmailRequest.endLinkEmailRequest(b));
 }
 
-export function encodeEmailConfirm(email: string, code: string): Uint8Array {
+export function encodeLinkEmailConfirm(email: string, code: string): Uint8Array {
   const b = new Builder(128);
   const e = b.createString(email);
   const c = b.createString(code);
-  fb.EmailConfirmRequest.startEmailConfirmRequest(b);
-  fb.EmailConfirmRequest.addEmail(b, e);
-  fb.EmailConfirmRequest.addCode(b, c);
-  return finish(b, fb.EmailConfirmRequest.endEmailConfirmRequest(b));
+  fb.LinkEmailConfirm.startLinkEmailConfirm(b);
+  fb.LinkEmailConfirm.addEmail(b, e);
+  fb.LinkEmailConfirm.addCode(b, c);
+  return finish(b, fb.LinkEmailConfirm.endLinkEmailConfirm(b));
+}
+
+export function encodeLinkTelegram(data: string): Uint8Array {
+  const b = new Builder(256);
+  const d = b.createString(data);
+  fb.LinkTelegramRequest.startLinkTelegramRequest(b);
+  fb.LinkTelegramRequest.addData(b, d);
+  return finish(b, fb.LinkTelegramRequest.endLinkTelegramRequest(b));
+}
+
+export function decodeLinkResult(buf: Uint8Array): LinkResult {
+  const r = fb.LinkResult.getRootAsLinkResult(new ByteBuffer(buf));
+  const sess = r.session();
+  return {
+    status: (s(r.status()) || 'linked') as LinkResult['status'],
+    secondaryUserId: s(r.secondaryUserId()),
+    secondaryDisplayName: s(r.secondaryDisplayName()),
+    secondaryGames: r.secondaryGames(),
+    secondaryFriends: r.secondaryFriends(),
+    session: sess
+      ? { token: s(sess.token()), userId: s(sess.userId()), isGuest: sess.isGuest(), displayName: s(sess.displayName()) }
+      : null,
+  };
 }
 
 // --- Stage 8 decoders ---