Add reversible administrator room archiving

Organize closed rooms with archive filters, live-authorized atomic receipts and exact saved retries. Preserve saved games, timestamps, credentials, discussion and AI deadlines. Unarchive leaves play closed; reopen requires unarchive, and removal/restoration preserves both flags.

Verified types, lint, 5379 offline tests, 52 HTTP tests and build. Twenty dedicated administrator HTTP groups and independent privacy/persistence review passed. Desktop/mobile browser QA confirmed a single archive after a lost response and refresh, readable recovery text, mobile unarchive and separate reopening, and saved-seat restoration. All 2,049 baseline rooms, 4,348 seats and related records preserved. Authenticated production admin acceptance awaits authorized QA access; full admin and rules gates remain open.

lib/admin-directory.ts

@@ -4,6 +4,7 @@ export type AdminRoom = {
   code: string;
   version: number;
   removed: boolean;
+  archived: boolean;
   updatedAt: number;
   status: 'lobby' | 'setup' | 'playing' | 'finished' | 'unreadable';
   host: string | null;