R6(a): de-stage code, docs, READMEs; split stage6_test

Mechanical, behaviour-preserving removal of Stage N / TODO-N / phase (RN)
references from comments, doc-comments, service READMEs, the current-state docs
(ARCHITECTURE, FUNCTIONAL+_ru, TESTING, UI_DESIGN), config-file comments, and the
.fbs/.proto schema comments. PLAN.md / PRERELEASE.md / CLAUDE.md keep the stage
history.

- Rename the only stage-named identifiers: registerStage8 -> registerSocialOps,
  registerStage11 -> registerLinkOps (gateway transcode).
- Split stage6_test.go: TestEmailLoginFlow -> email_test.go,
  TestGuestAutoMatchLeavesNoStats (+ provisionGuest) -> account_test.go.
- Regenerated proto bindings (push.pb.go, telegram_grpc.pb.go) from the de-staged
  .proto comments; FB Go/TS bindings unchanged (flatc strips schema comments).

go build/vet/gofmt clean across modules; integration typecheck and pnpm check green.

platform/telegram/README.md

@@ -34,7 +34,7 @@ route by an **operator-chosen** `language` (unrelated to login).
 - **Bot chat.** `/start <payload>` (and the chat menu button) reply with a Mini App
   launch button; a deep-link payload routes the launch to a game / invitation /
   friend code.
-- **Admin messaging** (wired in Stage 10). `SendToUser` and `SendToGameChannel` send
+- **Admin messaging.** `SendToUser` and `SendToGameChannel` send
   arbitrary text to one user or a game channel through the bot the request selects by
   `language` (an operator choice in the admin console).
 
@@ -47,7 +47,7 @@ Telegram-specific.
 
 `pkg/proto/telegram/v1`, service `Telegram`: `ValidateInitData`,
 `ValidateLoginWidget`, `Notify`, `SendToUser`, `SendToGameChannel`. Generated Go is
-committed under `pkg`. `ValidateLoginWidget` (Stage 11) verifies Telegram **Login
+committed under `pkg`. `ValidateLoginWidget` verifies Telegram **Login
 Widget** web sign-in data — HMAC under `SHA-256(bot_token)`, distinct from initData
 (`internal/loginwidget`) — for attaching a Telegram identity to an account from a
 browser.
@@ -103,7 +103,7 @@ all egress through a VPN sidecar (`deploy/docker-compose.yml`, mirroring
 `../../15-puzzle`). It needs no public ingress — it long-polls Telegram and answers
 internal gRPC at `telegram:9091` on the shared `edge` network. The host reverse proxy
 routes public traffic to the **gateway** port only, which serves the Mini App under
-`/telegram/`. The full multi-service deploy lands with Stage 12.
+`/telegram/`. The full multi-service deploy is `deploy/docker-compose.yml`.
 
 A real end-to-end Telegram smoke needs a BotFather bot, its token, a public HTTPS
 Mini App origin, and the connector container; the unit tests cover the wire format,