db: sql.js/Drizzle connection + atomic persist (empty schema)

Flight-Ops plumbing minus game code: in-memory WASM DB, persist() via tmp+rename,
globalThis singleton. Schema is empty at scaffold stage; _meta plumbing table stamps
created_at on first open so the ./db volume holds a valid SQLite file from boot
(a brand-new sql.js database exports as zero bytes). instrumentation.ts opens it at
server start behind a runtime-guarded dynamic import (keeps node:fs out of the Edge
instrumentation bundle).

lib/db/schema.ts

@@ -0,0 +1,6 @@
+// Drizzle schema for game state. EMPTY on purpose at scaffold stage (v0.1.0) — no game
+// tables yet; the first turn-engine/ship/crew tables land with the first game systems.
+// Column names/types here are the source of truth; matching CREATE TABLE statements live
+// in lib/db/client.ts (DDL) and must stay in sync with this file.
+
+export {};