Ready for a crowd: idle rooms sleep, share cards render once

Memory now carries only live tables — a sweep puts finished rooms to
bed after 30 minutes and anything untouched after a day, and getRoom
wakes a sleeping room from its ledger the moment anyone asks (the
seed plus the log IS the game). The room cap counts ledgers on disk,
not just rooms awake. Share-card PNGs render once per share id and
cache immutable. Rate-limit kicks use terminate() so an abuser cannot
hold the socket open by ignoring the closing handshake.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015RCWSTnb1KYTPyL4GmhGnF

packages/server/src/store.ts

@@ -97,6 +97,29 @@ export function appendLine(roomId: string, line: RoomLine): void {
   appendFileSync(fileFor(roomId), JSON.stringify(line) + "\n", "utf8");
 }
 
+/** Read one persisted room's lines, or null if it has no ledger. */
+export function readRoom(roomId: string): RoomLine[] | null {
+  const file = fileFor(roomId);
+  if (!existsSync(file)) return null;
+  try {
+    const lines = readFileSync(file, "utf8")
+      .split("\n")
+      .filter((l) => l.trim().length > 0)
+      .map((l) => JSON.parse(l) as RoomLine);
+    return lines.length > 0 && lines[0]!.kind === "meta" ? lines : null;
+  } catch (e) {
+    console.error(`unreadable room file ${roomId}:`, e);
+    return null;
+  }
+}
+
+/** How many rooms have ledgers on disk — the server-wide cap counts these,
+ * not just the rooms currently awake in memory. */
+export function countRoomFiles(): number {
+  ensureDataDir();
+  return readdirSync(DATA_DIR).filter((f) => f.endsWith(".jsonl")).length;
+}
+
 /** Read every persisted room's lines, keyed by room id. */
 export function readAllRooms(): Map<string, RoomLine[]> {
   ensureDataDir();