Emit floats an f32 can hold, and drop the format! that formats nothing

CI runs cargo fmt --check and clippy -D warnings, and this branch had
never been through either. Both would have failed it.

The bulk was the generated colour tables: eight significant figures where
an f32 carries about 7.2, so the eighth is noise that rounds away at
compile time and clippy's excessive_precision says so 109 times over.
Fixed in the generator rather than only in the file, so it stays fixed --
and the file is trimmed in place rather than re-derived, because
regenerating it needs a colour-science stack that has nothing to do with
the defect.

The format! in the composer is mine too, from extracting the rendering
tail: the braces in it were escaped because the text used to live inside a
larger template, and once extracted the escapes are noise and the call
formats nothing.

Also here, and clearly not mine: an unused import and a shadowed binding
in dr-gpu, and an unused import in a test. They are pre-existing --
clippy has been failing on master before this branch existed, on lints
like is_multiple_of that arrived with a toolchain rather than with
anyone's code. Fixed because CI cannot go green around them, and called
out because a merge commit is a bad place to quietly edit someone else's
crate.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

core/dr-gpu/tests/film_sim.rs

@@ -46,7 +46,12 @@ fn flat_raw(level: u16) -> RawImage {
         // leaving a curve here would test the suppression rather than the
         // film. `dr-pipeline` asserts the suppression on the generated source.
         base_curve: BaseCurve::IDENTITY,
-        crop: CropRect { x: 0, y: 0, width: SIZE, height: SIZE },
+        crop: CropRect {
+            x: 0,
+            y: 0,
+            width: SIZE,
+            height: SIZE,
+        },
     }
 }
 
@@ -166,5 +171,8 @@ fn a_negative_and_its_print_are_not_the_same_picture() {
     );
     let spread = printed.iter().cloned().fold(f32::MIN, f32::max)
         - printed.iter().cloned().fold(f32::MAX, f32::min);
-    assert!(spread < 0.06, "the print of a neutral is not neutral: {printed:?}");
+    assert!(
+        spread < 0.06,
+        "the print of a neutral is not neutral: {printed:?}"
+    );
 }