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.

docs/FUNCTIONAL.md

@@ -4,18 +4,17 @@ Per-domain user stories: what each user-visible operation does. This is the
 starting point for any change request that touches behaviour. The English
 version is authoritative; [`FUNCTIONAL_ru.md`](FUNCTIONAL_ru.md) is a mirror for
 the project owner — mirror every point edit in the same patch (translate only
-the changed paragraphs). Sections deepen as stages land; *(Stage N)* marks where
-the detail is authored.
+the changed paragraphs).
 
 ## Domains
 
-### Client app *(Stage 7 / 8)*
-The web/app client (Svelte + Vite) realizes these stories. The **playable slice**
-(Stage 7) covers signing in (guest or email), the "my games" lobby, starting an
+### Client app
+The web/app client (Svelte + Vite) realizes these stories. It
+covers signing in (guest or email), the "my games" lobby, starting an
 auto-match, playing the board (place tiles by drag or tap, pass, exchange, resign),
 the top-1 hint, the unlimited word-check with complaint, per-game chat and nudge,
 real-time in-app updates, switching interface language (en/ru) and theme, and a
-read-only profile. **Stage 8** adds managing friends (including one-time friend
+read-only profile. It also handles managing friends (including one-time friend
 codes) and blocks, friend-game invitations, editing the profile and binding an
 email, the statistics screen, and the in-game history viewer with GCG export.
 Settings also pick the board's bonus-label style (beginner / classic / none). A hint **lays the suggested tiles on the board** for the player to confirm and
@@ -26,7 +25,7 @@ theme, and links to the matching per-language Telegram channel; the game itself
 `/app/` (web) and `/telegram/` (the Telegram Mini App). The landing's theme is ephemeral
 (it follows the system scheme, not the saved preference); its language choice is saved.
 
-### Identity & sessions *(Stage 1 / 6 / 9 / 15)*
+### Identity & sessions
 A player arrives from a platform (Telegram first), via email login, or as an
 ephemeral guest. The gateway validates the credential once and mints a thin
 session token; the backend resolves it to an internal `user_id`. A **Telegram Mini
@@ -56,7 +55,7 @@ pause until it is back (a server-data screen still opens, with the spinner, and
 reconnect), and pending reads resume on their own — the interface stays usable instead of
 flashing a red banner each time.
 
-### Accounts, linking & merge *(Stage 1 / 11)*
+### Accounts, linking & merge
 First platform contact auto-provisions a durable account. From the profile a player
 links an email (via a confirm code) or their Telegram (via the web sign-in); a guest
 who links their first identity becomes a durable account. The "already taken" status
@@ -68,12 +67,12 @@ when a guest links an identity that already has a durable account, where the dur
 account is kept and the guest's games move into it. A merge is blocked only while the
 two accounts share a game still in progress.
 
-### Lobby & matchmaking *(Stage 4 / 15)*
+### Lobby & matchmaking
 Bottom tab menu: **my games**, **profile**. The **my games** list groups games into three
 sections — *your turn*, *opponent's turn* and *finished* (empty sections are hidden) — and
 orders them so the games awaiting your move come first, the longest-waiting on top, while
 opponent-turn and finished games are most-recent first; it renders as a compact,
-line-separated list (Stage 17). You can **remove a finished game from your own list**:
+line-separated list. You can **remove a finished game from your own list**:
 swipe a finished row left (or, on desktop, tap its **⋮**) to reveal a **❌**, then tap it.
 The removal is per-account and permanent — the game disappears only from your list and stays
 in the other players' lists, and there is no undo. The game types offered on **New Game** are
@@ -84,13 +83,13 @@ unrestricted). Variants are shown by their **display name** — both Scrabble va
 the same name titles the in-game screen. This gates only **starting** a new game — both auto-match and a friend
 invitation — so a player still sees and plays existing games of any language. Auto-match
 (always 2 players) joins a per-variant pool and is paired with the next waiting human;
-after 10 s with no human the robot substitutes (the robot arrives in Stage 5). Friend games (2–4) are
+after 10 s with no human the robot substitutes. Friend games (2–4) are
 formed by inviting players from the friend list (an invitation, like a friend code,
 is shareable as a Telegram deep link that opens it directly): the inviter chooses the
 settings and the game starts once every invitee has accepted — any decline cancels it, and an unanswered invitation
 expires after seven days.
 
-### Playing a game *(Stage 3)*
+### Playing a game
 Place tiles, pass, exchange, or resign. A play is validated against the game's
 dictionary at submit time and scored; an unlimited preview reports what a
 tentative move would score and whether it is legal. The dictionary check tool is
@@ -111,7 +110,7 @@ and restored on return (including on another device); a player may **arrange til
 the opponent's turn**, but that draft is position-only — the score preview and submission
 stay available only on the player's own turn.
 
-### Robot opponent *(Stage 5)*
+### Robot opponent
 When auto-match finds no human within ten seconds, a robot opponent takes the empty
 seat so the game starts without waiting. It is meant to feel like a person: it
 decides once per game whether to play to win (about 40% of the time, so the human
@@ -123,7 +122,7 @@ carries a human-like, language-appropriate name (a Russian game draws mostly Rus
 names); it does not chat, and **silently ignores friend requests** — a request to a
 robot stays pending and expires, exactly like a human who never responds.
 
-### Social: friends, block, chat, nudge *(Stage 4 / 8)*
+### Social: friends, block, chat, nudge
 Become friends in two ways: redeem a **one-time code** the other player issues (six
 digits, valid for twelve hours), or send a **request to someone you have played
 with** — they accept, ignore it (a request lapses after thirty days and can then be
@@ -132,7 +131,7 @@ a code). Cancelling your own pending request withdraws it; unfriending removes t
 friendship. In a game, an **add to friends** item for each opponent mirrors the live
 relationship: it reads *request sent* (disabled) while a request is pending or was
 declined, and *in friends* once accepted — updating in place the moment the opponent
-answers, and staying correct across reloads (Stage 17). Block globally — switch off incoming chat
+answers, and staying correct across reloads. Block globally — switch off incoming chat
 and/or friend requests — and block individual players (a per-user block hides that
 person's chat and stops requests and game invitations both ways; it also ends any
 existing friendship). Per-game chat is for quick reactions: messages are short
@@ -142,16 +141,16 @@ nudge is part of the game chat); the out-of-app push is delivered via the platfo
 Chat and the word-check tool open as their **own screens** (with a back to the game), and a
 new chat message raises an **unread badge** on the game's menu until the chat is opened.
 
-### Profile & settings *(Stage 4 / 8)*
+### Profile & settings
 Edit the display name (letters joined by a single space / "." / "_" separator, with an
 optional trailing ".", up to 32 characters and at most 5 special characters — the "." / "_"
 punctuation, spaces aside), the timezone (chosen as a UTC offset), the
 daily away window (on a 10-minute grid, at most 12 hours, wrapping midnight) and the
 block toggles. The profile form is edited inline (no separate edit mode). Linking
 an email or Telegram and merging accounts are covered under "Accounts, linking &
-merge" (Stage 11).
+merge".
 
-### History & statistics *(Stage 3 / 8)*
+### History & statistics
 Finished games are archived in a dictionary-independent form and exportable to
 GCG; the export is offered **only once a game is finished** (exporting a live game
 would leak the move journal), and the client shares the `.gcg` file where the
@@ -159,7 +158,7 @@ platform supports it, otherwise downloads it. Statistics (durable accounts only)
 wins, losses, draws, max points in a game, and max points for a single move (the
 best play, which already includes every word it formed plus the all-tiles bonus).
 
-### Administration *(Stage 10)*
+### Administration
 Operators reach a server-rendered admin console at `${DOMAIN}/_gm` — the backend
 renders it; the gateway gates it with HTTP Basic Auth on its public listener and
 proxies it verbatim. The console lists and inspects **users** (profile, statistics,
@@ -173,7 +172,7 @@ applied after a reload). When a Telegram connector is configured an operator can
 State-changing actions are protected by a same-origin check; the console tracks no
 operator identity.
 
-The console also surfaces **rate-limit abuse** (R3): a **Throttled** page lists the
+The console also surfaces **rate-limit abuse**: a **Throttled** page lists the
 recently throttled users/IPs the gateway reported (an in-memory window — it resets on
 a backend restart) and the accounts currently carrying the soft **high-rate flag**. An
 account sustaining rejections past a tunable threshold is flagged automatically —