feat(admin-ui): sub-room caps and test-case issue linking

Two admin screens for work that previously had server support but no way to
reach it.

Rooms → a room → Sub-rooms: per-sub-room max players, with the room's own
advertised capacity shown alongside so the two are not mistaken for each other.
Each row also shows whether the sub-room is a matchmaking target and which blob
it loads.

Activity → Test cases: file a GitHub issue against a case, follow the link, or
unlink it, plus a reconcile button. Filing is idempotent server-side, so the
button is safe to press twice. When GitHub is unconfigured the actions disable
themselves and the page explains why rather than failing on click — a server
with no token is an ordinary deployment.

Both go in as tabs on the existing hub pages rather than new sidebar entries,
matching how the nav is organised.

Server side adds GET api/admin/v1/testcases (the list the SPA renders, with
each case's issue number) and mirrors the three issue routes under
/api/admin/v1/testcases/... because the SPA's client speaks that prefix
exclusively.

I had told the user this UI was not possible on this branch because
wwwroot/admin holds a built bundle. That was wrong — the source is in
DorkNet.Server/admin-ui and builds to it.

DorkNet.Server/admin-ui/src/pages/Room.tsx

@@ -17,7 +17,7 @@ import { ArrowLeft, RefreshCw, Trash } from '../components/Icons';
 // modals: general info edit, owner / co-owner / mod / host
 // management, live photon instances, recent visitors, danger zone.
 
-type Tab = 'general' | 'roles' | 'instances' | 'leaderboards' | 'visitors' | 'danger';
+type Tab = 'general' | 'roles' | 'subrooms' | 'instances' | 'leaderboards' | 'visitors' | 'danger';
 
 const ROLE_LABEL: Record<0 | 1 | 2, string> = {
   0: 'Co-owner',
@@ -67,7 +67,7 @@ export function Room() {
         <>
           <RoomHeaderCard room={room} />
           <div className="flex gap-1 mt-4 mb-3 overflow-x-auto border-b border-ink-800">
-            {(['general', 'roles', 'instances', 'leaderboards', 'visitors', 'danger'] as Tab[]).map(t => (
+            {(['general', 'roles', 'subrooms', 'instances', 'leaderboards', 'visitors', 'danger'] as Tab[]).map(t => (
               <button
                 key={t}
                 onClick={() => setTab(t)}
@@ -79,6 +79,7 @@ export function Room() {
               >
                 {t === 'general' ? 'General' :
                  t === 'roles' ? 'Roles & ownership' :
+                 t === 'subrooms' ? 'Sub-rooms' :
                  t === 'instances' ? 'Live instances' :
                  t === 'leaderboards' ? 'Leaderboards' :
                  t === 'visitors' ? 'Recent visitors' :
@@ -89,6 +90,7 @@ export function Room() {
 
           {tab === 'general' && <GeneralTab room={room} onSaved={refresh} />}
           {tab === 'roles' && <RolesTab room={room} onChanged={refresh} />}
+          {tab === 'subrooms' && <SubRoomsTab roomId={room.id} roomCapacity={room.maxCapacity} />}
           {tab === 'instances' && <InstancesTab roomId={room.id} />}
           {tab === 'leaderboards' && <LeaderboardsTab roomId={room.id} />}
           {tab === 'visitors' && <VisitorsTab roomId={room.id} />}
@@ -553,6 +555,113 @@ function TransferOwnerModal({ room, onClose, onTransferred }: {
 
 // ── Instances tab — live photon matches in this room ────────────────────
 
+interface SubRoom {
+  id: string;
+  subRoomId: number;
+  name: string;
+  maxPlayers: number;
+  canMatchmakeInto: boolean;
+  isSandbox: boolean;
+  dataBlobName: string;
+}
+
+// Per-sub-room player caps. Distinct from the room's own MaxCapacity, which is
+// what the ROOM advertises and what matchmaking hands to
+// RoomInstance.MaxCapacity — each sub-room caps itself separately, and the two
+// are easy to conflate. The same value is editable in game by the room owner
+// ("Max Player Count in This Subroom"); this reaches rooms an admin does not
+// own.
+function SubRoomsTab({ roomId, roomCapacity }: { roomId: number; roomCapacity: number }) {
+  const toast = useToast();
+  const { data, loading, error, refresh } = useApi<SubRoom[]>(`/rooms/${roomId}/subrooms`);
+  const [edits, setEdits] = useState<Record<number, string>>({});
+  const [saving, setSaving] = useState<number | null>(null);
+
+  const save = async (sub: SubRoom) => {
+    const raw = edits[sub.subRoomId];
+    const value = Number(raw);
+    if (!Number.isInteger(value) || value < 1 || value > 80) {
+      toast.push('Max players must be a whole number between 1 and 80', 'error');
+      return;
+    }
+    setSaving(sub.subRoomId);
+    try {
+      await api(`/rooms/${roomId}/subrooms/${sub.subRoomId}/maxplayers`, {
+        method: 'PUT',
+        body: { MaxPlayers: value },
+      });
+      toast.push(`${sub.name || `Sub-room ${sub.subRoomId}`} capped at ${value}`, 'success');
+      setEdits(prev => {
+        const next = { ...prev };
+        delete next[sub.subRoomId];
+        return next;
+      });
+      refresh();
+    } catch (e) {
+      toast.push((e as Error).message, 'error');
+    } finally {
+      setSaving(null);
+    }
+  };
+
+  return (
+    <div className="card overflow-hidden">
+      <div className="flex items-center justify-between px-4 py-2.5 border-b border-ink-800">
+        <div className="text-xs text-ink-400">
+          Room advertises <span className="text-ink-200 font-medium">{roomCapacity}</span> — each
+          sub-room caps itself separately
+        </div>
+        <button onClick={refresh} className="btn-secondary text-xs" disabled={loading}>
+          <RefreshCw className={loading ? 'animate-spin' : ''} /> Refresh
+        </button>
+      </div>
+      {error && <div className="px-4 py-3 text-sm text-danger">{error}</div>}
+      {data && data.length === 0 && <Empty title="No sub-rooms" />}
+      {data && data.length > 0 && (
+        <ul className="divide-y divide-ink-800">
+          {data.map(sub => {
+            const pending = edits[sub.subRoomId];
+            const dirty = pending !== undefined && Number(pending) !== sub.maxPlayers;
+            return (
+              <li key={sub.id} className="px-4 py-3 flex flex-wrap items-center justify-between gap-3">
+                <div className="min-w-0">
+                  <div className="flex items-center gap-2">
+                    <span className="text-sm font-medium text-ink-50">{sub.name || '(unnamed)'}</span>
+                    <span className="badge-neutral">SubRoom {sub.subRoomId}</span>
+                    {sub.isSandbox && <span className="badge-neutral">Sandbox</span>}
+                    {!sub.canMatchmakeInto && <span className="badge-banned">No matchmaking</span>}
+                  </div>
+                  {sub.dataBlobName && (
+                    <div className="text-xs text-ink-500 font-mono truncate mt-0.5">{sub.dataBlobName}</div>
+                  )}
+                </div>
+                <div className="flex items-center gap-2">
+                  <label className="text-xs text-ink-400">Max players</label>
+                  <input
+                    type="number"
+                    min={1}
+                    max={80}
+                    value={pending ?? String(sub.maxPlayers)}
+                    onChange={e => setEdits(prev => ({ ...prev, [sub.subRoomId]: e.target.value }))}
+                    className="input w-20 text-sm"
+                  />
+                  <button
+                    onClick={() => save(sub)}
+                    disabled={!dirty || saving === sub.subRoomId}
+                    className="btn-primary text-xs"
+                  >
+                    {saving === sub.subRoomId ? 'Saving…' : 'Save'}
+                  </button>
+                </div>
+              </li>
+            );
+          })}
+        </ul>
+      )}
+    </div>
+  );
+}
+
 function InstancesTab({ roomId }: { roomId: number }) {
   const toast = useToast();
   const { data, loading, error, refresh } = useApi<RoomInstance[]>(`/rooms/${roomId}/instances`);