Reflow what rustfmt wanted in the raw histogram

The author could not run cargo, so this is the formatter's first pass
over the new module and its presentation half.

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

core/dr-gpu/src/raw_histogram.rs

@@ -595,7 +595,11 @@ mod tests {
         // the axis were inverted the histogram would still look like a
         // histogram, and every headroom judgement made from it would be
         // exactly backwards.
-        assert_eq!(RawHistogram::stops(BINS - 1), 0.0, "the top bin is saturation");
+        assert_eq!(
+            RawHistogram::stops(BINS - 1),
+            0.0,
+            "the top bin is saturation"
+        );
         assert_eq!(RawHistogram::stops(BINS - 1 - BINS_PER_STOP), 1.0);
         assert_eq!(RawHistogram::stops(BINS - 1 - 8 * BINS_PER_STOP), 8.0);
         // The floor is one bin short of `STOPS`, because bin 0 is the end of
@@ -704,7 +708,11 @@ mod tests {
             );
             // Neutral, so the brightest channel must land on the same bin as
             // the three do.
-            assert_eq!(hist.brightest()[bin], h, "the envelope drifted at bin {bin}");
+            assert_eq!(
+                hist.brightest()[bin],
+                h,
+                "the envelope drifted at bin {bin}"
+            );
         }
         // Nothing below the ramp, so an off-by-one that spilled a pixel past
         // the end of it would show here rather than hiding in a bin the loop
@@ -742,7 +750,11 @@ mod tests {
         let hist = pass.compute(&source(&ctx, &rgb, 4, 1)).expect("compute");
 
         assert_eq!(hist.pixels(), 4);
-        assert_eq!(hist.saturated(), 2, "two pixels have a channel at the ceiling");
+        assert_eq!(
+            hist.saturated(),
+            2,
+            "two pixels have a channel at the ceiling"
+        );
         assert_eq!(hist.at_black(), 0);
         assert_eq!(hist.red()[BINS - 1], 2);