fix(base): a queue drain allocates nothing - two lists, reused

The rest of the leak Physics found: a drain that carried facts gave its list away and made a new
one, every queue every frame something happened. The queue keeps two lists and hands one out while
the other fills; a drained list is good until the next drain of that queue (nothing in the game or
the packages keeps one past it). With ab34f82's empty drain and in-place clear, a queue allocates
nothing in steady state. queue_test holds the reuse; every package (403) and lab/unit (90) pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.base/tests/queue_test.ludic

@@ -87,6 +87,23 @@ program QueueTest {
   }
 
   test "a queue drains in the order it was pushed" () { fifo_case() }
+  # two lists, reused: a drained list is the caller's until the next drain of that queue
+  function reuse_case() -> void {
+    let q: Queue<int> = queue_new("reused")
+    q_push(q, 1)
+    let a = q_drain(q)
+    q_push(q, 2)
+    expect_eq(a[0], 1)
+    let b = q_drain(q)
+    expect_eq(b[0], 2)
+    q_push(q, 3)
+    let c = q_drain(q)
+    expect(c == a)
+    expect_eq(len(c), 1)
+    expect_eq(c[0], 3)
+  }
+
+  test "a drain reuses the queue's two lists" () { reuse_case() }
   test "an empty drain allocates nothing, and a drained list is the caller's" () { empty_case() }
   test "a queue holds records" () { record_case() }
   test "clear drops what is waiting" () { clear_case() }