Keep the test scene's own arithmetic from overflowing a u64

The first compile this branch ever had. `cargo fmt` reflowed four files
and clippy passed at -D warnings untouched, but one test panicked:
`the_signature_does_not_change_with_scale`, on "attempt to multiply with
overflow".

It is the fixture, not the feature. `scene()`'s little LCG multiplied the
block's y by the golden-ratio constant with a plain `*` while the term
beside it already used `wrapping_mul`, so any scene taller than about 104
pixels overflowed in debug. Only the scale test builds one that large,
which is why 345 of 346 passed around it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/dr-ui/src/bursts.rs

@@ -179,11 +179,7 @@ thread_local! {
 /// Deliberately silent otherwise. The sweeps around it report progress because
 /// they run for tens of minutes; this is seconds, and a status line for it would
 /// be a line the user must read in order to learn nothing.
-pub fn start_pass(
-    catalog_path: PathBuf,
-    thumbs_dir: PathBuf,
-    grouped: impl Fn(usize) + 'static,
-) {
+pub fn start_pass(catalog_path: PathBuf, thumbs_dir: PathBuf, grouped: impl Fn(usize) + 'static) {
     // A second pass would read the same rows and write the same answer over the
     // first one's transactions.
     if RUNNING.get() {