chore(workspace): satisfy clippy --all-targets in test code

Five test-only lints surfaced by --all-targets were blocking CI under
-D warnings: a useless vec! in a leaderboard sort test, a
field_reassign_with_default in tuning tests, and three
assertions_on_constants in card_plugin sanity tests. The constant
assertions are now wrapped in const blocks so they run at compile time;
the runtime-formatted values were dropped from their messages because
const-block assert messages must be string literals.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

solitaire_engine/src/card_animation/tuning.rs

@@ -210,8 +210,10 @@ mod tests {
 
     #[test]
     fn scale_duration_applies_multiplier() {
-        let mut t = AnimationTuning::default();
-        t.duration_scale = 0.5;
+        let t = AnimationTuning {
+            duration_scale: 0.5,
+            ..AnimationTuning::default()
+        };
         assert!((t.scale_duration(1.0) - 0.5).abs() < 1e-6);
         assert!((t.scale_duration(0.25) - 0.125).abs() < 1e-6);
     }