mail UI: dedupe broadcast fan-out and drop in-game admin compose

Two issues surfaced once the long-lived dev environment finally
reached the diplomail view:

1. `/sent` returns one row per recipient for broadcast and admin
   fan-outs (so the admin tooling can render the materialised
   audience). The list pane fed all rows into the stand-alone
   bucket, so the `{#each entries as e (entryKey(e))}` key in
   `thread-list.svelte` collapsed to the same `standalone:${id}`
   for every recipient and Svelte 5 aborted the render with
   `each_key_duplicate`. Dedupe stand-alones by `message_id` in
   `buildEntries`.

2. The compose dialog exposed an `admin` kind toggle gated on
   "owner of game". That was a Phase 28 plan decision, but admin
   compose is an operator tool (server admin), not an in-game
   action — every game owner should not be able to broadcast
   admin notifications. Drop the admin option, the audience
   sub-toggles, and the admin path through `submit`. The
   `MailStore.composeAdmin` wrapper and the backend RPC stay so
   the future admin UI can call them.

Vitest covers the fan-out dedup with three rows sharing one
`message_id` collapsing to a single stand-alone entry.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/frontend/src/lib/active-view/mail/compose.svelte

@@ -1,8 +1,10 @@
 <!--
 Phase 28 — compose dialog for diplomatic mail. The recipient picker
-reads `gameState.report.races[]` (Phase 22), the kind toggle exposes
-personal / broadcast / admin; broadcast and admin sends are gated
-server-side, the UI surfaces the resulting 403 inline.
+reads `gameState.report.races[]` (Phase 22); the kind toggle exposes
+personal / broadcast. The admin compose path lives in the
+server-side admin tooling, not in the in-game UI, so it is not
+surfaced here. Broadcast sends are gated server-side; the UI
+surfaces the resulting 403 inline.
 -->
 <script lang="ts">
 	import { getContext } from "svelte";
@@ -14,8 +16,7 @@ server-side, the UI surfaces the resulting 403 inline.
 		type RenderedReportSource,
 	} from "$lib/rendered-report.svelte";
 
-	type ComposeKind = "personal" | "broadcast" | "admin";
-	type AdminAudience = "active" | "active_and_removed" | "all_members";
+	type ComposeKind = "personal" | "broadcast";
 
 	let {
 		onClose,
@@ -39,8 +40,6 @@ server-side, the UI surfaces the resulting 403 inline.
 
 	let kind = $state<ComposeKind>("personal");
 	let raceName = $state("");
-	let adminTarget = $state<"user" | "all">("user");
-	let adminAudience = $state<AdminAudience>("active");
 	let subject = $state("");
 	let body = $state("");
 	let error = $state<string | null>(null);
@@ -60,8 +59,7 @@ server-side, the UI surfaces the resulting 403 inline.
 			error = i18n.t("game.mail.body_required");
 			return;
 		}
-		const needsRecipient = kind === "personal" || (kind === "admin" && adminTarget === "user");
-		if (needsRecipient && raceName === "") {
+		if (kind === "personal" && raceName === "") {
 			error = i18n.t("game.mail.recipient_required");
 			return;
 		}
@@ -76,18 +74,7 @@ server-side, the UI surfaces the resulting 403 inline.
 				onSent(raceName);
 				return;
 			}
-			if (kind === "broadcast") {
-				await mailStore.composeBroadcast({ subject, body: bodyText });
-				onSent(null);
-				return;
-			}
-			await mailStore.composeAdmin({
-				target: adminTarget,
-				raceName: adminTarget === "user" ? raceName : undefined,
-				recipients: adminTarget === "all" ? adminAudience : undefined,
-				subject,
-				body: bodyText,
-			});
+			await mailStore.composeBroadcast({ subject, body: bodyText });
 			onSent(null);
 		} catch (err) {
 			error = err instanceof Error ? err.message : String(err);
@@ -109,31 +96,10 @@ server-side, the UI surfaces the resulting 403 inline.
 			<select bind:value={kind} data-testid="mail-compose-kind">
 				<option value="personal">{i18n.t("game.mail.compose.target_personal")}</option>
 				<option value="broadcast">{i18n.t("game.mail.compose.target_broadcast")}</option>
-				<option value="admin">{i18n.t("game.mail.compose.target_admin")}</option>
 			</select>
 		</label>
 
-		{#if kind === "admin"}
-			<label>
-				{i18n.t("game.mail.compose.recipients_label")}
-				<select bind:value={adminTarget} data-testid="mail-compose-admin-target">
-					<option value="user">{i18n.t("game.mail.compose.target_personal")}</option>
-					<option value="all">{i18n.t("game.mail.compose.target_broadcast")}</option>
-				</select>
-			</label>
-			{#if adminTarget === "all"}
-				<label>
-					{i18n.t("game.mail.compose.recipients_label")}
-					<select bind:value={adminAudience} data-testid="mail-compose-admin-audience">
-						<option value="active">{i18n.t("game.mail.compose.recipients_active")}</option>
-						<option value="active_and_removed">{i18n.t("game.mail.compose.recipients_active_and_removed")}</option>
-						<option value="all_members">{i18n.t("game.mail.compose.recipients_all_members")}</option>
-					</select>
-				</label>
-			{/if}
-		{/if}
-
-		{#if kind === "personal" || (kind === "admin" && adminTarget === "user")}
+		{#if kind === "personal"}
 			<label>
 				{i18n.t("game.mail.recipient_label")}
 				<select bind:value={raceName} data-testid="mail-compose-recipient">

ui/frontend/src/lib/mail-store.svelte.ts

@@ -317,9 +317,24 @@ function buildEntries(inbox: MailMessage[], sent: MailMessage[]): MailListEntry[
 		thread.latestAt = last.createdAt;
 	}
 
+	// Broadcast and admin fan-outs return one row per recipient from
+	// the `/sent` endpoint (so the admin UI sees the materialised
+	// audience). The in-game list pane collapses them by `message_id`
+	// — without this dedupe the {#each} key in `thread-list.svelte`
+	// repeats and Svelte 5 aborts the render with `each_key_duplicate`.
+	const seen = new Set<string>();
+	const dedupedStandalones: MailStandalone[] = [];
+	for (const s of standalones) {
+		if (seen.has(s.message.messageId)) {
+			continue;
+		}
+		seen.add(s.message.messageId);
+		dedupedStandalones.push(s);
+	}
+
 	const entries: MailListEntry[] = [
 		...Array.from(threadsByRace.values()),
-		...standalones,
+		...dedupedStandalones,
 	];
 	entries.sort((a, b) => b.latestAt.getTime() - a.latestAt.getTime());
 	return entries;