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-pipeline/src/lib.rs

@@ -112,11 +112,11 @@ mod tests {
             stock: "test_stock".into(),
             print: None,
             tables: crate::ops::FilmTables {
-            exposure_matrix: [[5.0, 0.5, 0.2], [0.1, 5.0, 0.3], [0.2, 0.5, 4.0]],
-            curves: vec![[0.5, 0.5, 0.5]; crate::ops::film_sim::CURVE_SAMPLES],
-            curve_log_min: -3.0,
-            curve_log_max: 4.0,
-            lut: vec![[0.5, 0.5, 0.5]; 32 * 32 * 32],
+                exposure_matrix: [[5.0, 0.5, 0.2], [0.1, 5.0, 0.3], [0.2, 0.5, 4.0]],
+                curves: vec![[0.5, 0.5, 0.5]; crate::ops::film_sim::CURVE_SAMPLES],
+                curve_log_min: -3.0,
+                curve_log_max: 4.0,
+                lut: vec![[0.5, 0.5, 0.5]; 32 * 32 * 32],
                 density_max: 3.0,
                 lut_size: 32,
             },