fix(social): robot blocks

Blocking an auto-match opponent who is secretly a pooled robot is recorded  instead in a separate `robot_blocks` table.

Now blocking behaves the same in that game (struck name, hidden composer) and lists the blocked opponent under the name you saw, but is recorded only against that game — the disguise holds, the shared robot is never globally blocked, and the matchmaker keeps pairing you with robots (so you can never block yourself out of opponents).

- the shared robot account is never put in `blocks`
- the matchmaker keeps it free and it is not blocked under its other per-game names
- the blocked list and the in-game card still show it by joining that table; an unblock deletes the row

PRERELEASE.md

@@ -35,7 +35,7 @@ the edge before prod. Each phase maps back to the owner's raw pre-release TODO l
 | AD | Advertising banner ("ad network"): server-driven weighted campaigns (percent weight + validity window; the perpetual default fills the remainder up to 100%), bilingual messages shown by bot (`service_language`); eligibility = free account + empty hint wallet + no `no_banner` role (guests included); the resolved feed rides `profile.get` with a `notify` `banner` re-poll on eligibility change; `/_gm/banners` admin + global display timings; client smooth-weighted-round-robin rotation + fade-out/gap/fade-in UX. A single `app.load` bootstrap aggregator was considered and **deferred** (see ARCHITECTURE §10). | owner ad-hoc | **done** (PR1 backend+admin, PR2 UI rotation) |
 | GL | Simultaneous quick-game cap (10): grey "New Game" + a lobby notice at the cap; backend gate on quick enqueue + invitation creation (409 `game_limit_reached`), accepting invitations exempt; `at_game_limit` rides `games.list` | owner ad-hoc | **done** |
 | CR | In-game chat read receipts: per-message `unread_seats` bitmask (migration `00008`); a per-viewer unread **dot** in the lobby + game header (a nudge counts and clears when its recipient moves); reading = opening the move history (the 💬 fade-blinks twice) or the chat, acked (`chat.read`) only when unread; `chat_read_duration` + `chat_unread_messages` metrics + tracing + the **Scrabble — Messages** Grafana dashboard (follow-up PR); a message to a disguised robot opponent is born read; admin unread-only filter / read column / per-seat read card | owner ad-hoc | **done** |
-| BX | Asymmetric per-user block + in-game controls: a block now silently suppresses everything **from** the blocked user (chat, nudge, friend requests, invitations are kept but never delivered/surfaced, born-read) while they notice nothing, **without** deleting the friendship (unblock restores it); auto-match excludes a block-related pair (either direction); in-game opponent card gains a ✖️ **block** control (mirroring 🤝, red "Block?" confirm, mutual-hide, struck name + hidden chat composer when blocked); optimistic apply + `user_blocked`/`user_unblocked` event confirm + rollback; admin user card gains **blocks / blocked-by / friends** cross-linked lists | owner ad-hoc | **done** |
+| BX | Asymmetric per-user block + in-game controls: a block now silently suppresses everything **from** the blocked user (chat, nudge, friend requests, invitations are kept but never delivered/surfaced, born-read) while they notice nothing, **without** deleting the friendship (unblock restores it); auto-match excludes a block-related pair (either direction); in-game opponent card gains a ✖️ **block** control (mirroring 🤝, red "Block?" confirm, mutual-hide, struck name + hidden chat composer when blocked); optimistic apply + `user_blocked`/`user_unblocked` event confirm + rollback; admin user card gains **blocks / blocked-by / friends** cross-linked lists. Blocking a disguised-robot opponent is recorded per-game in a separate **`robot_blocks`** table (migration `00011`), keyed on game+seat with the seen name — never the shared robot account — so the matchmaker keeps giving robots; it shows in the blocked list and re-marks the in-game card | owner ad-hoc | **done** |
 | → | Stage 18 — prod contour deploy | — | see [`PLAN.md`](PLAN.md) |
 
 ## Key findings (these reshaped the raw list — read before starting a phase)