The sand hash moves with the grid it is over

screen-width and screen-height went from 1400x1000 to 900x600, and the first
colour changed. Those are defconsts the checker consumes to size rows and cols,
so the grid is a different shape and the hash over it is a different number.
Updated rather than reverted: the change is deliberate and the hash is a
regression test for the simulation being reproducible, not for it being any
particular size.

Checked the way the old number was: -2851001042534928384 on native and on
wasm32, byte for byte. A hash that moved on only one target would mean the
change had broken reproducibility rather than the grid, which is the thing this
case exists to catch.

NEXT.md

@@ -139,7 +139,7 @@ reader ✅ → parse ✅ → load ✅ → check ✅ → emit ✅ → clang ✅
 $ flan run calc-me.flan "1 + 2 * (3 - 0.5) / 2"
 3.5
 $ flan run test/programs/sand-headless.flan
-2256461126764447066
+-2851001042534928384
 $ flan run sand.flan                      # a window, 120 fps, hold space
 ```
 
@@ -1277,7 +1277,7 @@ and changing one's type is a silent mismatch against storage the host already la
 Deferred until after the dev loop:
 
 6. ~~**wasm32.**~~ **Done, with one glued joint.** `flan build --target=wasm32-wasi` produces a module, and
-`test/programs/sand-headless.flan` prints `2256461126764447066` under it — the same hash as native, byte for byte, at
+`test/programs/sand-headless.flan` prints `-2851001042534928384` under it — the same hash as native, byte for byte, at
 `-O2` and at `-O0`. That is the milestone: the RNG is ours rather than libc's precisely so that number can be compared
 across targets, and it compares equal. `values.flan` and `machine.flan` run there too, which is where a 32-bit pointer
 would have shown. The acceptance table runs all four, and skips them by *probing* — it builds the smallest program and

test/test_acceptance.ml

@@ -361,7 +361,7 @@ let () =
        and not raylib, deliberately — a program that imports raylib links
        libraylib on every target, and this one is the version meant to run on
        wasm32 too. The hash is reproducible only because rand-f32 is ours. *)
-    let sand_out = "2256461126764447066\n" in
+    let sand_out = "-2851001042534928384\n" in
     outputs "sand, headless" "programs/sand-headless.flan" sand_out;
     outputs ~opt:"-O0" "sand, headless, -O0" "programs/sand-headless.flan" sand_out;