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.

gateway/internal/backendclient/api.go

@@ -35,7 +35,7 @@ type ProfileResp struct {
 	NotificationsInAppOnly bool   `json:"notifications_in_app_only"`
 }
 
-// LinkResultResp is the result of an account link/merge step (Stage 11). Status is
+// LinkResultResp is the result of an account link/merge step. Status is
 // "linked", "merge_required" (the secondary_* fields summarise the other account) or
 // "merged". Token is a switched-session token (a guest initiator's durable
 // counterpart won); Profile is the surviving/active account's profile.
@@ -50,7 +50,7 @@ type LinkResultResp struct {
 }
 
 // TileJSON is one tile in a decoded move response (history, move result, hint); its Letter
-// is a concrete character (Stage 13 keeps the move journal in letters).
+// is a concrete character (the move journal is kept in letters).
 type TileJSON struct {
 	Row    int    `json:"row"`
 	Col    int    `json:"col"`
@@ -58,7 +58,7 @@ type TileJSON struct {
 	Blank  bool   `json:"blank"`
 }
 
-// PlayTileJSON is one inbound tile to place, addressed by alphabet index (Stage 13). For a
+// PlayTileJSON is one inbound tile to place, addressed by alphabet index. For a
 // blank, Letter is the designated letter's index and Blank is true.
 type PlayTileJSON struct {
 	Row    int  `json:"row"`
@@ -107,7 +107,7 @@ type GameResp struct {
 }
 
 // MoveResultResp is the outcome of a committed move. Rack carries the actor's refilled rack as
-// wire alphabet indices and BagLen the bag size after the draw (R4).
+// wire alphabet indices and BagLen the bag size after the draw.
 type MoveResultResp struct {
 	Move   MoveRecordResp `json:"move"`
 	Game   GameResp       `json:"game"`
@@ -116,14 +116,14 @@ type MoveResultResp struct {
 }
 
 // AlphabetEntryJSON is one letter of a variant's alphabet (its index, concrete letter and
-// tile value), present in StateResp only when the client requested it (Stage 13).
+// tile value), present in StateResp only when the client requested it.
 type AlphabetEntryJSON struct {
 	Index  int    `json:"index"`
 	Letter string `json:"letter"`
 	Value  int    `json:"value"`
 }
 
-// StateResp is a player's view of a game. Rack carries wire alphabet indices (Stage 13);
+// StateResp is a player's view of a game. Rack carries wire alphabet indices;
 // Alphabet is present only when the request asked for it.
 type StateResp struct {
 	Game           GameResp            `json:"game"`
@@ -224,7 +224,7 @@ func (c *Client) Profile(ctx context.Context, userID string) (ProfileResp, error
 }
 
 // SubmitPlay commits a placement on the player's turn. The tiles are addressed by alphabet
-// index (Stage 13).
+// index.
 func (c *Client) SubmitPlay(ctx context.Context, userID, gameID, dir string, tiles []PlayTileJSON) (MoveResultResp, error) {
 	var out MoveResultResp
 	body := map[string]any{"dir": dir, "tiles": tiles}
@@ -233,7 +233,7 @@ func (c *Client) SubmitPlay(ctx context.Context, userID, gameID, dir string, til
 }
 
 // GameState returns the player's view of a game. When includeAlphabet is set the backend
-// embeds the variant's alphabet table (Stage 13); the client asks for it on a per-variant
+// embeds the variant's alphabet table; the client asks for it on a per-variant
 // cache miss only.
 func (c *Client) GameState(ctx context.Context, userID, gameID string, includeAlphabet bool) (StateResp, error) {
 	var out StateResp
@@ -320,7 +320,7 @@ func (c *Client) Pass(ctx context.Context, userID, gameID string) (MoveResultRes
 }
 
 // Exchange swaps the chosen rack tiles back into the bag. Tiles are wire alphabet indices
-// (Stage 13; a blank is engine.BlankIndex).
+// (a blank is engine.BlankIndex).
 func (c *Client) Exchange(ctx context.Context, userID, gameID string, tiles []int) (MoveResultResp, error) {
 	var out MoveResultResp
 	err := c.do(ctx, http.MethodPost, c.gamePath(gameID, "/exchange"), userID, "",
@@ -342,7 +342,7 @@ func (c *Client) Hint(ctx context.Context, userID, gameID string) (HintResultRes
 	return out, err
 }
 
-// GetDraft returns the player's saved composition for a game (Stage 17) as the backend's
+// GetDraft returns the player's saved composition for a game as the backend's
 // raw JSON body. The gateway forwards it verbatim, never interpreting its shape.
 func (c *Client) GetDraft(ctx context.Context, userID, gameID string) (json.RawMessage, error) {
 	var out json.RawMessage
@@ -350,21 +350,21 @@ func (c *Client) GetDraft(ctx context.Context, userID, gameID string) (json.RawM
 	return out, err
 }
 
-// SaveDraft upserts the player's composition for a game (Stage 17). body is the client's
+// SaveDraft upserts the player's composition for a game. body is the client's
 // {rack_order, board_tiles} JSON, forwarded verbatim — a json.RawMessage marshals as-is, so
 // there is no double-encode.
 func (c *Client) SaveDraft(ctx context.Context, userID, gameID string, body json.RawMessage) error {
 	return c.do(ctx, http.MethodPut, c.gamePath(gameID, "/draft"), userID, "", body, nil)
 }
 
-// HideGame hides a finished game from the caller's own games list (Stage 17). The action is
+// HideGame hides a finished game from the caller's own games list. The action is
 // per-account and irreversible; the game stays visible to the other players.
 func (c *Client) HideGame(ctx context.Context, userID, gameID string) error {
 	return c.do(ctx, http.MethodPost, c.gamePath(gameID, "/hide"), userID, "", struct{}{}, nil)
 }
 
 // Evaluate previews a tentative play's legality and score. The tiles are addressed by
-// alphabet index (Stage 13).
+// alphabet index.
 func (c *Client) Evaluate(ctx context.Context, userID, gameID, dir string, tiles []PlayTileJSON) (EvalResultResp, error) {
 	var out EvalResultResp
 	err := c.do(ctx, http.MethodPost, c.gamePath(gameID, "/evaluate"), userID, "",
@@ -373,7 +373,7 @@ func (c *Client) Evaluate(ctx context.Context, userID, gameID, dir string, tiles
 }
 
 // CheckWord looks a word up in the game's pinned dictionary. The word is carried as
-// repeated ?idx= alphabet indices (Stage 13); the backend echoes the decoded concrete word.
+// repeated ?idx= alphabet indices; the backend echoes the decoded concrete word.
 func (c *Client) CheckWord(ctx context.Context, userID, gameID string, word []int) (WordCheckResp, error) {
 	var out WordCheckResp
 	q := url.Values{}

gateway/internal/backendclient/api_social.go

@@ -6,7 +6,7 @@ import (
 	"net/url"
 )
 
-// The Stage 8 response structs and client methods mirror the backend's social,
+// The response structs and client methods mirror the backend's social,
 // account and history JSON DTOs. The transcode layer maps them to FlatBuffers.
 
 // AccountRefResp is a referenced account with its display name resolved.
@@ -249,7 +249,7 @@ func (c *Client) LinkEmailRequest(ctx context.Context, userID, email string) err
 }
 
 // LinkEmailConfirm verifies the code and binds a free email or reports a required
-// merge (Stage 11).
+// merge.
 func (c *Client) LinkEmailConfirm(ctx context.Context, userID, email, code string) (LinkResultResp, error) {
 	var out LinkResultResp
 	err := c.do(ctx, http.MethodPost, "/api/v1/user/link/email/confirm", userID, "",
@@ -257,7 +257,7 @@ func (c *Client) LinkEmailConfirm(ctx context.Context, userID, email, code strin
 	return out, err
 }
 
-// LinkEmailMerge re-verifies the code and performs the merge (Stage 11).
+// LinkEmailMerge re-verifies the code and performs the merge.
 func (c *Client) LinkEmailMerge(ctx context.Context, userID, email, code string) (LinkResultResp, error) {
 	var out LinkResultResp
 	err := c.do(ctx, http.MethodPost, "/api/v1/user/link/email/merge", userID, "",
@@ -266,7 +266,7 @@ func (c *Client) LinkEmailMerge(ctx context.Context, userID, email, code string)
 }
 
 // LinkTelegram attaches a gateway-validated Telegram identity to the caller or
-// reports a required merge (Stage 11).
+// reports a required merge.
 func (c *Client) LinkTelegram(ctx context.Context, userID, externalID string) (LinkResultResp, error) {
 	var out LinkResultResp
 	err := c.do(ctx, http.MethodPost, "/api/v1/user/link/telegram", userID, "",
@@ -275,7 +275,7 @@ func (c *Client) LinkTelegram(ctx context.Context, userID, externalID string) (L
 }
 
 // LinkTelegramMerge merges the account owning a gateway-validated Telegram identity
-// into the caller's (Stage 11).
+// into the caller's.
 func (c *Client) LinkTelegramMerge(ctx context.Context, userID, externalID string) (LinkResultResp, error) {
 	var out LinkResultResp
 	err := c.do(ctx, http.MethodPost, "/api/v1/user/link/telegram/merge", userID, "",

gateway/internal/backendclient/client.go

@@ -129,7 +129,7 @@ func (c *Client) SubscribePush(ctx context.Context, gatewayID string) (grpc.Serv
 // ReportRateLimited posts the gateway's periodic rate-limiter rejection summary
 // to the backend, which feeds the admin console's throttled view and the
 // high-rate auto-flag. The endpoint carries no user identity: like
-// sessions/resolve it rides the trusted internal segment (R3).
+// sessions/resolve it rides the trusted internal segment.
 func (c *Client) ReportRateLimited(ctx context.Context, windowSeconds int, entries []ratelimit.Rejection) error {
 	body := struct {
 		WindowSeconds int                   `json:"window_seconds"`