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-film/src/lib.rs

@@ -37,8 +37,8 @@
 //! `tools/film-profiles/convert.py` rather than pasted, so what changed is
 //! auditable. The sRGB reflectance basis is Mallett & Yuksel (2019).
 
-mod built_in;
 pub mod bake;
+mod built_in;
 pub mod profile;
 pub mod spectrum;
 pub mod tables;
@@ -97,7 +97,11 @@ mod tests {
 
     #[test]
     fn every_built_in_profile_parses() {
-        assert_eq!(built_in().len(), BUILT_IN.len(), "a built-in profile failed to parse");
+        assert_eq!(
+            built_in().len(),
+            BUILT_IN.len(),
+            "a built-in profile failed to parse"
+        );
     }
 
     #[test]