feat(api): GET /api/events endpoint + OpenAPI

Latest game events, newest first; auto-initializes like the other reads.
?limit= defaults to 50 (cap 200), non-integer/out-of-range → 400. OpenAPI
spec gains the path + Event schema (14 -> 15 paths).

app/api/events/route.ts

@@ -0,0 +1,21 @@
+import { getGameDb } from '@/lib/db/client'
+import { ensureSave } from '@/lib/game/save'
+import { EventError, getEvents, parseEventLimit } from '@/lib/game/events'
+
+// The latest game events, newest first; auto-initializes on first hit.
+export async function GET(req: Request) {
+  const db = await getGameDb()
+  await ensureSave(db) // getEvents assumes a save exists
+
+  let limit: number
+  try {
+    limit = parseEventLimit(new URL(req.url).searchParams.get('limit'))
+  } catch (err) {
+    if (err instanceof EventError) {
+      return Response.json({ error: err.message }, { status: err.status })
+    }
+    throw err
+  }
+
+  return Response.json(await getEvents(db, limit))
+}