ludic.things: a removed Thing's record placed again, oldest first past a lag of 32; things_reserve sizes the grid once

thing_put and thing_spawn made a new record for every Thing placed, and the world places and removes
them all day (an animal's sign and bed, a drop, a fish), so play grew by a record per placement.
Removed records wait in a queue compacted in place; once 32 wait, the oldest is set back as new
with a new uid. ludic.base's grid_reserve makes the buckets for n rows now, since a rehash in play
leaves the old bucket array behind. Tests: a record comes back only past the lag, as new, with a
new uid, the indexes agree, and the spare queue stays bounded.

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

packages/ludic.things/tests/things_test.ludic

@@ -215,4 +215,30 @@ program ThingsTest {
     expect(out[0] == a)
     expect_eq(things_changed(things_st, seen, rows, out), 2)
   }
+  test "a removed Thing's record is placed again once enough wait, as new, with a new uid" (things_st: mut ThingsState) {
+    things_reset(things_st)
+    let first = thing_put(things_st, TH_LURE, "lure", 1.0, 1.0, 0.0, 0.0, 2.0, 7)
+    first.used = 5
+    first.owner = 3
+    thing_hide(first)
+    let old_uid = first.uid
+    thing_remove(things_st, first)
+    for i in 0 .. 32 { thing_remove(things_st, thing_put(things_st, TH_BRANCH, "branch", float(i), 0.0, 0.0, 0.0, 1.5, 0)) }
+    expect_eq(things_spare_count(things_st), 33)
+    let again = thing_put(things_st, TH_SIGN, "sign", 4.0, 4.0, 0.0, 0.0, 2.0, 1)
+    let ap: pointer = again
+    let fp: pointer = first
+    expect(ap == fp)
+    expect(again.uid != old_uid)
+    expect_eq(again.kind, TH_SIGN)
+    expect_eq(again.used, 0)
+    expect_eq(again.owner, -1)
+    expect(again.active)
+    expect_eq(thing_nearest(things_st, TH_SIGN, 4.0, 4.0).uid, again.uid)
+    expect_eq(things_verify(things_st), 0)
+    for i in 0 .. 500 { thing_remove(things_st, thing_put(things_st, TH_BRANCH, "branch", 0.0, float(i), 0.0, 0.0, 1.5, 0)) }
+    expect(things_spare_count(things_st) <= 33)
+    things_reserve(things_st, 5000)
+    expect_eq(things_verify(things_st), 0)
+  }
 }